diff --git a/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/IntExpression.cs b/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/IntExpression.cs
index f44eb093bf2..2d249670a08 100644
--- a/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/IntExpression.cs
+++ b/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/IntExpression.cs
@@ -8,5 +8,17 @@ namespace AutoRest.CSharp.Common.Output.Expressions.KnownValueExpressions
     internal sealed record IntExpression(ValueExpression Untyped) : TypedValueExpression<int>(Untyped)
     {
         public static IntExpression MaxValue => new(StaticProperty(nameof(int.MaxValue)));
+
+        public IntExpression Add(IntExpression value) => Operator("+", value);
+        public IntExpression Minus(IntExpression value) => Operator("-", value);
+        public IntExpression Multiply(IntExpression value) => Operator("*", value);
+        public IntExpression DivideBy(IntExpression value) => Operator("/", value);
+
+        public static IntExpression operator +(IntExpression left, IntExpression right) => left.Add(right);
+        public static IntExpression operator -(IntExpression left, IntExpression right) => left.Minus(right);
+        public static IntExpression operator *(IntExpression left, IntExpression right) => left.Multiply(right);
+        public static IntExpression operator /(IntExpression left, IntExpression right) => left.DivideBy(right);
+
+        private IntExpression Operator(string op, IntExpression other) => new(new BinaryOperatorExpression(op, this, other));
     }
 }
diff --git a/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/StringBuilderExpression.cs b/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/StringBuilderExpression.cs
index 5fb476f3bf5..ea9e54f4026 100644
--- a/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/StringBuilderExpression.cs
+++ b/src/AutoRest.CSharp/Common/Output/Expressions/KnownValueExpressions/StringBuilderExpression.cs
@@ -10,7 +10,7 @@ namespace AutoRest.CSharp.Common.Output.Expressions.KnownValueExpressions
 {
     internal sealed record StringBuilderExpression(ValueExpression Untyped) : TypedValueExpression<StringBuilder>(Untyped)
     {
-        public StringExpression Length => new(Property(nameof(StringBuilder.Length)));
+        public IntExpression Length => new(Property(nameof(StringBuilder.Length)));
 
         public MethodBodyStatement Append(StringExpression value) => new InvokeInstanceMethodStatement(Untyped, nameof(StringBuilder.Append), value);
 
@@ -27,5 +27,7 @@ internal sealed record StringBuilderExpression(ValueExpression Untyped) : TypedV
         public MethodBodyStatement Append(FormattableStringExpression value) => new InvokeInstanceMethodStatement(Untyped, nameof(StringBuilder.Append), value);
 
         public MethodBodyStatement AppendLine(FormattableStringExpression value) => new InvokeInstanceMethodStatement(Untyped, nameof(StringBuilder.AppendLine), value);
+
+        public MethodBodyStatement Remove(ValueExpression startIndex, ValueExpression length) => new InvokeInstanceMethodStatement(Untyped, nameof(StringBuilder.Remove), startIndex, length);
     }
 }
diff --git a/src/AutoRest.CSharp/Common/Output/Expressions/ValueExpressions/IndexerExpression.cs b/src/AutoRest.CSharp/Common/Output/Expressions/ValueExpressions/IndexerExpression.cs
index 19d4c756b6a..965d3942036 100644
--- a/src/AutoRest.CSharp/Common/Output/Expressions/ValueExpressions/IndexerExpression.cs
+++ b/src/AutoRest.CSharp/Common/Output/Expressions/ValueExpressions/IndexerExpression.cs
@@ -1,7 +1,6 @@
 // Copyright(c) Microsoft Corporation.All rights reserved.
 // Licensed under the MIT License.
 
-using System;
 using AutoRest.CSharp.Generation.Writers;
 
 namespace AutoRest.CSharp.Common.Output.Expressions.ValueExpressions
diff --git a/src/AutoRest.CSharp/Common/Output/Models/Types/HelperTypeProviders/System/ClientUriBuilderProvider.cs b/src/AutoRest.CSharp/Common/Output/Models/Types/HelperTypeProviders/System/ClientUriBuilderProvider.cs
index acc3b458254..9e46a80f054 100644
--- a/src/AutoRest.CSharp/Common/Output/Models/Types/HelperTypeProviders/System/ClientUriBuilderProvider.cs
+++ b/src/AutoRest.CSharp/Common/Output/Models/Types/HelperTypeProviders/System/ClientUriBuilderProvider.cs
@@ -10,7 +10,6 @@
 using AutoRest.CSharp.Common.Output.Expressions.ValueExpressions;
 using AutoRest.CSharp.Common.Output.Models;
 using AutoRest.CSharp.Generation.Types;
-using AutoRest.CSharp.Output.Models.Serialization;
 using AutoRest.CSharp.Output.Models.Shared;
 using static AutoRest.CSharp.Common.Output.Models.Snippets;
 
@@ -32,14 +31,12 @@ private ClientUriBuilderProvider() : base(Configuration.HelperNamespace, null)
         private readonly FieldDeclaration _uriBuilderField = new(FieldModifiers.Private, typeof(UriBuilder), "_uriBuilder");
         private readonly FieldDeclaration _pathBuilderField = new(FieldModifiers.Private, typeof(StringBuilder), "_pathBuilder");
         private readonly FieldDeclaration _queryBuilderField = new(FieldModifiers.Private, typeof(StringBuilder), "_queryBuilder");
-        private readonly FieldDeclaration _pathSeparatorField = new(FieldModifiers.Private | FieldModifiers.Const, typeof(char), "PathSeparator", Literal('/'), SerializationFormat.Default);
 
         protected override IEnumerable<FieldDeclaration> BuildFields()
         {
             yield return _uriBuilderField;
             yield return _pathBuilderField;
             yield return _queryBuilderField;
-            yield return _pathSeparatorField;
         }
 
         private PropertyDeclaration? _uriBuilderProperty;
@@ -156,9 +153,9 @@ private IEnumerable<Method> BuildAppendPathMethods()
                     Assign(value, new InvokeStaticMethodExpression(typeof(Uri), nameof(Uri.EscapeDataString), new[]{ value }))
                 },
                 EmptyLine,
-                new IfStatement(Equal(new IndexerExpression(value, Literal(0)), _pathSeparatorField))
+                new IfStatement(And(And(GreaterThan(pathBuilder.Length, Int(0)), Equal(new IndexerExpression(pathBuilder, pathBuilder.Length - Int(1)), Literal('/'))), Equal(new IndexerExpression(value, Int(0)), Literal('/'))))
                 {
-                    Assign(value, value.Substring(Literal(1)))
+                    pathBuilder.Remove(pathBuilder.Length - Int(1), Int(1))
                 },
                 EmptyLine,
                 pathBuilder.Append(value),
diff --git a/test/CadlRanchProjectsNonAzure/authentication/http/custom/src/Generated/Internal/ClientUriBuilder.cs b/test/CadlRanchProjectsNonAzure/authentication/http/custom/src/Generated/Internal/ClientUriBuilder.cs
index df0eff3a7f0..f1aefb52089 100644
--- a/test/CadlRanchProjectsNonAzure/authentication/http/custom/src/Generated/Internal/ClientUriBuilder.cs
+++ b/test/CadlRanchProjectsNonAzure/authentication/http/custom/src/Generated/Internal/ClientUriBuilder.cs
@@ -14,7 +14,6 @@ internal class ClientUriBuilder
         private UriBuilder _uriBuilder;
         private StringBuilder _pathBuilder;
         private StringBuilder _queryBuilder;
-        private const char PathSeparator = '/';
 
         public ClientUriBuilder()
         {
@@ -42,9 +41,9 @@ public void AppendPath(string value, bool escape)
                 value = Uri.EscapeDataString(value);
             }
 
-            if (value[0] == PathSeparator)
+            if (PathBuilder.Length > 0 && PathBuilder[PathBuilder.Length - 1] == '/' && value[0] == '/')
             {
-                value = value.Substring(1);
+                PathBuilder.Remove(PathBuilder.Length - 1, 1);
             }
 
             PathBuilder.Append(value);
diff --git a/test/UnbrandedProjects.Tests/ClientUriBuilderTests.cs b/test/UnbrandedProjects.Tests/ClientUriBuilderTests.cs
new file mode 100644
index 00000000000..87948b403c0
--- /dev/null
+++ b/test/UnbrandedProjects.Tests/ClientUriBuilderTests.cs
@@ -0,0 +1,461 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Collections.Generic;
+using NUnit.Framework;
+using UnbrandedTypeSpec;
+
+namespace UnbrandedProjects.Tests
+{
+    public class ClientUriBuilderTests
+    {
+        [TestCase("http://localhost", null, "http://localhost/")]
+        [TestCase("http://localhost/", null, "http://localhost/")]
+        [TestCase("http://localhost:12345", null, "http://localhost:12345/")]
+        [TestCase("http://localhost:12345/", null, "http://localhost:12345/")]
+        [TestCase("http://localhost/with", null, "http://localhost/with")]
+        [TestCase("http://localhost/with/", null, "http://localhost/with/")]
+        [TestCase("http://localhost:12345/with", null, "http://localhost:12345/with")]
+        [TestCase("http://localhost:12345/with/", null, "http://localhost:12345/with/")]
+        [TestCase("http://localhost", "path", "http://localhost/path")]
+        [TestCase("http://localhost/", "path", "http://localhost/path")]
+        [TestCase("http://localhost:12345", "path", "http://localhost:12345/path")]
+        [TestCase("http://localhost:12345/", "path", "http://localhost:12345/path")]
+        [TestCase("http://localhost/with", "path", "http://localhost/withpath")]
+        [TestCase("http://localhost/with/", "path", "http://localhost/with/path")]
+        [TestCase("http://localhost:12345/with", "path", "http://localhost:12345/withpath")]
+        [TestCase("http://localhost:12345/with/", "path", "http://localhost:12345/with/path")]
+        [TestCase("http://localhost", "/path", "http://localhost/path")]
+        [TestCase("http://localhost/", "/path", "http://localhost/path")]
+        [TestCase("http://localhost:12345", "/path", "http://localhost:12345/path")]
+        [TestCase("http://localhost:12345/", "/path", "http://localhost:12345/path")]
+        [TestCase("http://localhost/with", "/path", "http://localhost/with/path")]
+        [TestCase("http://localhost/with/", "/path", "http://localhost/with/path")]
+        [TestCase("http://localhost:12345/with", "/path", "http://localhost:12345/with/path")]
+        [TestCase("http://localhost:12345/with/", "/path", "http://localhost:12345/with/path")]
+        [TestCase("http://localhost", "/path/", "http://localhost/path/")]
+        [TestCase("http://localhost/", "/path/", "http://localhost/path/")]
+        [TestCase("http://localhost:12345", "/path/", "http://localhost:12345/path/")]
+        [TestCase("http://localhost:12345/", "/path/", "http://localhost:12345/path/")]
+        [TestCase("http://localhost/with", "/path/", "http://localhost/with/path/")]
+        [TestCase("http://localhost/with/", "/path/", "http://localhost/with/path/")]
+        [TestCase("http://localhost:12345/with", "/path/", "http://localhost:12345/with/path/")]
+        [TestCase("http://localhost:12345/with/", "/path/", "http://localhost:12345/with/path/")]
+        public void ResetThenAppendPath(string endpoint, string pathPart, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            if (pathPart != null)
+            {
+                builder.AppendPath(pathPart, false);
+            }
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "one|1", "http://localhost/?one=1")]
+        [TestCase("http://localhost:12345", "one|1", "http://localhost:12345/?one=1")]
+        [TestCase("http://localhost/some", "one|1", "http://localhost/some?one=1")]
+        [TestCase("http://localhost:12345/some", "one|1", "http://localhost:12345/some?one=1")]
+        [TestCase("http://localhost/", "one|1", "http://localhost/?one=1")]
+        [TestCase("http://localhost:12345/", "one|1", "http://localhost:12345/?one=1")]
+        [TestCase("http://localhost/some/", "one|1", "http://localhost/some/?one=1")]
+        [TestCase("http://localhost:12345/some/", "one|1", "http://localhost:12345/some/?one=1")]
+        [TestCase("http://localhost", "one|1|two|2", "http://localhost/?one=1&two=2")]
+        [TestCase("http://localhost:12345", "one|1|two|2", "http://localhost:12345/?one=1&two=2")]
+        [TestCase("http://localhost/some", "one|1|two|2", "http://localhost/some?one=1&two=2")]
+        [TestCase("http://localhost:12345/some", "one|1|two|2", "http://localhost:12345/some?one=1&two=2")]
+        [TestCase("http://localhost/", "one|1|two|2", "http://localhost/?one=1&two=2")]
+        [TestCase("http://localhost:12345/", "one|1|two|2", "http://localhost:12345/?one=1&two=2")]
+        [TestCase("http://localhost/some/", "one|1|two|2", "http://localhost/some/?one=1&two=2")]
+        [TestCase("http://localhost:12345/some/", "one|1|two|2", "http://localhost:12345/some/?one=1&two=2")]
+        public void ResetThenAppendQuery(string endpoint, string queryPart, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            if (queryPart != null)
+            {
+                var parts = queryPart.Split('|');
+                for (int i = 0; i < parts.Length; i += 2)
+                {
+                    builder.AppendQuery(parts[i], parts[i + 1], false);
+                }
+            }
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "some", "one|1", "http://localhost/some?one=1")]
+        [TestCase("http://localhost:12345", "some", "one|1", "http://localhost:12345/some?one=1")]
+        [TestCase("http://localhost/", "some/", "one|1", "http://localhost/some/?one=1")]
+        [TestCase("http://localhost:12345", "some/", "one|1", "http://localhost:12345/some/?one=1")]
+        [TestCase("http://localhost/", "/some", "one|1", "http://localhost/some?one=1")]
+        [TestCase("http://localhost:12345", "/some", "one|1", "http://localhost:12345/some?one=1")]
+        [TestCase("http://localhost/", "/some/", "one|1", "http://localhost/some/?one=1")]
+        [TestCase("http://localhost:12345", "/some/", "one|1", "http://localhost:12345/some/?one=1")]
+        [TestCase("http://localhost", "/some", "one|1|two|2", "http://localhost/some?one=1&two=2")]
+        [TestCase("http://localhost:12345", "/some", "one|1|two|2", "http://localhost:12345/some?one=1&two=2")]
+        [TestCase("http://localhost", "some/", "one|1|two|2", "http://localhost/some/?one=1&two=2")]
+        [TestCase("http://localhost:12345", "some/", "one|1|two|2", "http://localhost:12345/some/?one=1&two=2")]
+        [TestCase("http://localhost", "/some/", "one|1|two|2", "http://localhost/some/?one=1&two=2")]
+        [TestCase("http://localhost:12345", "/some/", "one|1|two|2", "http://localhost:12345/some/?one=1&two=2")]
+        public void ResetThenAppendPathThenAppendQuery(string endpoint, string pathPart, string queryPart, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            if (pathPart != null)
+            {
+                builder.AppendPath(pathPart, false);
+            }
+
+            if (queryPart != null)
+            {
+                var parts = queryPart.Split('|');
+                for (int i = 0; i < parts.Length; i += 2)
+                {
+                    builder.AppendQuery(parts[i], parts[i + 1], false);
+                }
+            }
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "some", "one|1", "http://localhost/some?one=1")]
+        [TestCase("http://localhost:12345", "some", "one|1", "http://localhost:12345/some?one=1")]
+        [TestCase("http://localhost/", "some/", "one|1", "http://localhost/some/?one=1")]
+        [TestCase("http://localhost:12345", "some/", "one|1", "http://localhost:12345/some/?one=1")]
+        [TestCase("http://localhost/", "/some", "one|1", "http://localhost/some?one=1")]
+        [TestCase("http://localhost:12345", "/some", "one|1", "http://localhost:12345/some?one=1")]
+        [TestCase("http://localhost/", "/some/", "one|1", "http://localhost/some/?one=1")]
+        [TestCase("http://localhost:12345", "/some/", "one|1", "http://localhost:12345/some/?one=1")]
+        [TestCase("http://localhost", "/some", "one|1|two|2", "http://localhost/some?one=1&two=2")]
+        [TestCase("http://localhost:12345", "/some", "one|1|two|2", "http://localhost:12345/some?one=1&two=2")]
+        [TestCase("http://localhost", "some/", "one|1|two|2", "http://localhost/some/?one=1&two=2")]
+        [TestCase("http://localhost:12345", "some/", "one|1|two|2", "http://localhost:12345/some/?one=1&two=2")]
+        [TestCase("http://localhost", "/some/", "one|1|two|2", "http://localhost/some/?one=1&two=2")]
+        [TestCase("http://localhost:12345", "/some/", "one|1|two|2", "http://localhost:12345/some/?one=1&two=2")]
+        public void ResetThenAppendQueryThenAppendPath(string endpoint, string pathPart, string queryPart, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            if (queryPart != null)
+            {
+                var parts = queryPart.Split('|');
+                for (int i = 0; i < parts.Length; i += 2)
+                {
+                    builder.AppendQuery(parts[i], parts[i + 1], false);
+                }
+            }
+
+            if (pathPart != null)
+            {
+                builder.AppendPath(pathPart, false);
+            }
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", true, true, "http://localhost/true")]
+        [TestCase("http://localhost", true, false, "http://localhost/true")]
+        [TestCase("http://localhost", false, true, "http://localhost/false")]
+        [TestCase("http://localhost", false, false, "http://localhost/false")]
+        public void AppendPath_Bool(string endpoint, bool value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendPath(value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 3.14f, true, "http://localhost/3.14")]
+        [TestCase("http://localhost", 3.14f, false, "http://localhost/3.14")]
+        [TestCase("http://localhost", -3.14f, true, "http://localhost/-3.14")]
+        [TestCase("http://localhost", -3.14f, false, "http://localhost/-3.14")]
+        public void AppendPath_Float(string endpoint, float value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendPath(value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 3.14, true, "http://localhost/3.14")]
+        [TestCase("http://localhost", 3.14, false, "http://localhost/3.14")]
+        [TestCase("http://localhost", -3.14, true, "http://localhost/-3.14")]
+        [TestCase("http://localhost", -3.14, false, "http://localhost/-3.14")]
+        public void AppendPath_Double(string endpoint, double value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendPath(value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 299792458, true, "http://localhost/299792458")]
+        [TestCase("http://localhost", 299792458, false, "http://localhost/299792458")]
+        [TestCase("http://localhost", -299792458, true, "http://localhost/-299792458")]
+        [TestCase("http://localhost", -299792458, false, "http://localhost/-299792458")]
+        public void AppendPath_Int(string endpoint, int value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendPath(value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 299792458000000, true, "http://localhost/299792458000000")]
+        [TestCase("http://localhost", 299792458000000, false, "http://localhost/299792458000000")]
+        [TestCase("http://localhost", -299792458000000, true, "http://localhost/-299792458000000")]
+        [TestCase("http://localhost", -299792458000000, false, "http://localhost/-299792458000000")]
+        public void AppendPath_Long(string endpoint, long value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendPath(value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "U", true, "http://localhost/aGVsbG8")]
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "D", true, "http://localhost/aGVsbG8%3D")]
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "U", false, "http://localhost/aGVsbG8")]
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "D", false, "http://localhost/aGVsbG8=")]
+        public void AppendPath_ByteArray(string endpoint, byte[] value, string format, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendPath(value, format, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", new[] { "hello", "world" }, true, "http://localhost/hello%2Cworld")]
+        [TestCase("http://localhost", new[] { "hello", "world" }, false, "http://localhost/hello,world")]
+        public void AppendPath_StringArray(string endpoint, IEnumerable<string> value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendPath(value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "D", true, "http://localhost/1905-06-30")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "U", true, "http://localhost/-2035622760")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "O", true, "http://localhost/1905-06-30T13%3A14%3A00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "o", true, "http://localhost/1905-06-30T13%3A14%3A00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "R", true, "http://localhost/Fri%2C 30 Jun 1905 13%3A14%3A00 GMT")] // TODO -- why spaces are not escaped?
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "D", false, "http://localhost/1905-06-30")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "U", false, "http://localhost/-2035622760")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "O", false, "http://localhost/1905-06-30T13:14:00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "o", false, "http://localhost/1905-06-30T13:14:00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "R", false, "http://localhost/Fri, 30 Jun 1905 13:14:00 GMT")]
+        public void AppendPath_DateTimeOffset(string endpoint, string value, string format, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            var dateTimeOffset = DateTimeOffset.Parse(value);
+            builder.AppendPath(dateTimeOffset, format, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "02:15:00", "P", true, "http://localhost/PT2H15M")]
+        [TestCase("http://localhost", "02:15:00", "", true, "http://localhost/02%3A15%3A00")]
+        [TestCase("http://localhost", "02:15:00", null, true, "http://localhost/PT2H15M")]
+        [TestCase("http://localhost", "02:15:00", "P", false, "http://localhost/PT2H15M")]
+        [TestCase("http://localhost", "02:15:00", "", false, "http://localhost/02:15:00")]
+        [TestCase("http://localhost", "02:15:00", null, false, "http://localhost/PT2H15M")]
+        public void AppendPath_TimeSpan(string endpoint, string value, string format, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            var timeSpan = TimeSpan.Parse(value);
+            builder.AppendPath(timeSpan, format, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "3f2504e0-4f89-11d3-9a0c-0305e82c3301", true, "http://localhost/3f2504e0-4f89-11d3-9a0c-0305e82c3301")]
+        [TestCase("http://localhost", "3f2504e0-4f89-11d3-9a0c-0305e82c3301", false, "http://localhost/3f2504e0-4f89-11d3-9a0c-0305e82c3301")]
+        public void AppendPath_Guid(string endpoint, string value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            var guid = Guid.Parse(value);
+            builder.AppendPath(guid, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", true, true, "http://localhost/?query=true")]
+        [TestCase("http://localhost", true, false, "http://localhost/?query=true")]
+        [TestCase("http://localhost", false, true, "http://localhost/?query=false")]
+        [TestCase("http://localhost", false, false, "http://localhost/?query=false")]
+        public void AppendQuery_Bool(string endpoint, bool value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendQuery("query", value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 3.14f, true, "http://localhost/?query=3.14")]
+        [TestCase("http://localhost", 3.14f, false, "http://localhost/?query=3.14")]
+        [TestCase("http://localhost", -3.14f, true, "http://localhost/?query=-3.14")]
+        [TestCase("http://localhost", -3.14f, false, "http://localhost/?query=-3.14")]
+        public void AppendQuery_Float(string endpoint, float value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendQuery("query", value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 3.14, true, "http://localhost/?query=3.14")]
+        [TestCase("http://localhost", 3.14, false, "http://localhost/?query=3.14")]
+        [TestCase("http://localhost", -3.14, true, "http://localhost/?query=-3.14")]
+        [TestCase("http://localhost", -3.14, false, "http://localhost/?query=-3.14")]
+        public void AppendQuery_Double(string endpoint, double value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendQuery("query", value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 299792458, true, "http://localhost/?query=299792458")]
+        [TestCase("http://localhost", 299792458, false, "http://localhost/?query=299792458")]
+        [TestCase("http://localhost", -299792458, true, "http://localhost/?query=-299792458")]
+        [TestCase("http://localhost", -299792458, false, "http://localhost/?query=-299792458")]
+        public void AppendQuery_Int(string endpoint, int value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendQuery("query", value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", 299792458000000, true, "http://localhost/?query=299792458000000")]
+        [TestCase("http://localhost", 299792458000000, false, "http://localhost/?query=299792458000000")]
+        [TestCase("http://localhost", -299792458000000, true, "http://localhost/?query=-299792458000000")]
+        [TestCase("http://localhost", -299792458000000, false, "http://localhost/?query=-299792458000000")]
+        public void AppendQuery_Long(string endpoint, long value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendQuery("query", value, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "U", true, "http://localhost/?query=aGVsbG8")]
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "D", true, "http://localhost/?query=aGVsbG8%3D")]
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "U", false, "http://localhost/?query=aGVsbG8")]
+        [TestCase("http://localhost", new byte[] { 104, 101, 108, 108, 111 }, "D", false, "http://localhost/?query=aGVsbG8=")]
+        public void AppendQuery_ByteArray(string endpoint, byte[] value, string format, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendQuery("query", value, format, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "D", true, "http://localhost/?query=1905-06-30")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "U", true, "http://localhost/?query=-2035622760")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "O", true, "http://localhost/?query=1905-06-30T13%3A14%3A00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "o", true, "http://localhost/?query=1905-06-30T13%3A14%3A00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "R", true, "http://localhost/?query=Fri%2C 30 Jun 1905 13%3A14%3A00 GMT")] // TODO -- why spaces are not escaped?
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "D", false, "http://localhost/?query=1905-06-30")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "U", false, "http://localhost/?query=-2035622760")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "O", false, "http://localhost/?query=1905-06-30T13:14:00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "o", false, "http://localhost/?query=1905-06-30T13:14:00.0000000Z")]
+        [TestCase("http://localhost", "6/30/1905 1:14:00 PM +00:00", "R", false, "http://localhost/?query=Fri, 30 Jun 1905 13:14:00 GMT")]
+        public void AppendQuery_DateTimeOffset(string endpoint, string value, string format, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            var dateTimeOffset = DateTimeOffset.Parse(value);
+            builder.AppendQuery("query", dateTimeOffset, format, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "02:15:00", "P", true, "http://localhost/?query=PT2H15M")]
+        [TestCase("http://localhost", "02:15:00", "", true, "http://localhost/?query=02%3A15%3A00")]
+        [TestCase("http://localhost", "02:15:00", null, true, "http://localhost/?query=PT2H15M")]
+        [TestCase("http://localhost", "02:15:00", "P", false, "http://localhost/?query=PT2H15M")]
+        [TestCase("http://localhost", "02:15:00", "", false, "http://localhost/?query=02:15:00")]
+        [TestCase("http://localhost", "02:15:00", null, false, "http://localhost/?query=PT2H15M")]
+        public void AppendQuery_TimeSpan(string endpoint, string value, string format, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            var timeSpan = TimeSpan.Parse(value);
+            builder.AppendQuery("query", timeSpan, format, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", "3f2504e0-4f89-11d3-9a0c-0305e82c3301", true, "http://localhost/?query=3f2504e0-4f89-11d3-9a0c-0305e82c3301")]
+        [TestCase("http://localhost", "3f2504e0-4f89-11d3-9a0c-0305e82c3301", false, "http://localhost/?query=3f2504e0-4f89-11d3-9a0c-0305e82c3301")]
+        public void AppendQuery_Guid(string endpoint, string value, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            var guid = Guid.Parse(value);
+            builder.AppendQuery("query", guid, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+
+        [TestCase("http://localhost", new[] { "hello", "world" }, ",", true, "http://localhost/?query=hello%2Cworld")]
+        [TestCase("http://localhost", new[] { "hello", "world" }, ";", true, "http://localhost/?query=hello%3Bworld")]
+        [TestCase("http://localhost", new[] { "hello", "world" }, "|", true, "http://localhost/?query=hello|world")]
+        [TestCase("http://localhost", new[] { "hello", "world" }, ",", false, "http://localhost/?query=hello,world")]
+        [TestCase("http://localhost", new[] { "hello", "world" }, ";", false, "http://localhost/?query=hello;world")]
+        [TestCase("http://localhost", new[] { "hello", "world" }, "|", false, "http://localhost/?query=hello|world")]
+        public void AppendQueryDelimited(string endpoint, IEnumerable<string> value, string delimiter, bool escape, string expected)
+        {
+            var builder = new ClientUriBuilder();
+            builder.Reset(new Uri(endpoint));
+
+            builder.AppendQueryDelimited("query", value, delimiter, escape);
+
+            Assert.AreEqual(expected, builder.ToUri().ToString());
+        }
+    }
+}
diff --git a/test/UnbrandedProjects/Customized-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs b/test/UnbrandedProjects/Customized-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
index 13d01eec7fc..465e6b237e5 100644
--- a/test/UnbrandedProjects/Customized-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
+++ b/test/UnbrandedProjects/Customized-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
@@ -14,7 +14,6 @@ internal class ClientUriBuilder
         private UriBuilder _uriBuilder;
         private StringBuilder _pathBuilder;
         private StringBuilder _queryBuilder;
-        private const char PathSeparator = '/';
 
         public ClientUriBuilder()
         {
@@ -42,9 +41,9 @@ public void AppendPath(string value, bool escape)
                 value = Uri.EscapeDataString(value);
             }
 
-            if (value[0] == PathSeparator)
+            if (PathBuilder.Length > 0 && PathBuilder[PathBuilder.Length - 1] == '/' && value[0] == '/')
             {
-                value = value.Substring(1);
+                PathBuilder.Remove(PathBuilder.Length - 1, 1);
             }
 
             PathBuilder.Append(value);
diff --git a/test/UnbrandedProjects/NoTest-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs b/test/UnbrandedProjects/NoTest-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
index cf3544d4971..9975f9d0308 100644
--- a/test/UnbrandedProjects/NoTest-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
+++ b/test/UnbrandedProjects/NoTest-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
@@ -14,7 +14,6 @@ internal class ClientUriBuilder
         private UriBuilder _uriBuilder;
         private StringBuilder _pathBuilder;
         private StringBuilder _queryBuilder;
-        private const char PathSeparator = '/';
 
         public ClientUriBuilder()
         {
@@ -42,9 +41,9 @@ public void AppendPath(string value, bool escape)
                 value = Uri.EscapeDataString(value);
             }
 
-            if (value[0] == PathSeparator)
+            if (PathBuilder.Length > 0 && PathBuilder[PathBuilder.Length - 1] == '/' && value[0] == '/')
             {
-                value = value.Substring(1);
+                PathBuilder.Remove(PathBuilder.Length - 1, 1);
             }
 
             PathBuilder.Append(value);
diff --git a/test/UnbrandedProjects/Platform-OpenAI-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs b/test/UnbrandedProjects/Platform-OpenAI-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
index b24daf5251a..2f5fd8765f8 100644
--- a/test/UnbrandedProjects/Platform-OpenAI-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
+++ b/test/UnbrandedProjects/Platform-OpenAI-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
@@ -14,7 +14,6 @@ internal class ClientUriBuilder
         private UriBuilder _uriBuilder;
         private StringBuilder _pathBuilder;
         private StringBuilder _queryBuilder;
-        private const char PathSeparator = '/';
 
         public ClientUriBuilder()
         {
@@ -42,9 +41,9 @@ public void AppendPath(string value, bool escape)
                 value = Uri.EscapeDataString(value);
             }
 
-            if (value[0] == PathSeparator)
+            if (PathBuilder.Length > 0 && PathBuilder[PathBuilder.Length - 1] == '/' && value[0] == '/')
             {
-                value = value.Substring(1);
+                PathBuilder.Remove(PathBuilder.Length - 1, 1);
             }
 
             PathBuilder.Append(value);
diff --git a/test/UnbrandedProjects/Unbranded-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs b/test/UnbrandedProjects/Unbranded-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
index bcdf8d4f529..798b4d78cf0 100644
--- a/test/UnbrandedProjects/Unbranded-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
+++ b/test/UnbrandedProjects/Unbranded-TypeSpec/src/Generated/Internal/ClientUriBuilder.cs
@@ -14,7 +14,6 @@ internal class ClientUriBuilder
         private UriBuilder _uriBuilder;
         private StringBuilder _pathBuilder;
         private StringBuilder _queryBuilder;
-        private const char PathSeparator = '/';
 
         public ClientUriBuilder()
         {
@@ -42,9 +41,9 @@ public void AppendPath(string value, bool escape)
                 value = Uri.EscapeDataString(value);
             }
 
-            if (value[0] == PathSeparator)
+            if (PathBuilder.Length > 0 && PathBuilder[PathBuilder.Length - 1] == '/' && value[0] == '/')
             {
-                value = value.Substring(1);
+                PathBuilder.Remove(PathBuilder.Length - 1, 1);
             }
 
             PathBuilder.Append(value);