diff --git a/runtime/CSharp/tests/issue-3510/ChannelTest.g4 b/runtime/CSharp/tests/issue-3510/ChannelTest.g4
new file mode 100644
index 0000000000..27947a253f
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/ChannelTest.g4
@@ -0,0 +1,7 @@
+grammar ChannelTest;
+
+prog : INT+ EOF;
+INT : [0-9]+;
+AAA : [a-z]+ -> channel(HIDDEN); // Note--lowercase "channel"
+BBB : [A-Z]+ -> Channel(HIDDEN); // Note--uppercase "Channel"
+WS : [ \t\r\n] -> skip;
diff --git a/runtime/CSharp/tests/issue-3510/ErrorListener.cs b/runtime/CSharp/tests/issue-3510/ErrorListener.cs
new file mode 100644
index 0000000000..1d610a3b56
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/ErrorListener.cs
@@ -0,0 +1,18 @@
+using Antlr4.Runtime;
+using Antlr4.Runtime.Misc;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+public class ErrorListener<S> : ConsoleErrorListener<S>
+{
+    public bool had_error;
+
+    public override void SyntaxError(TextWriter output, IRecognizer recognizer, S offendingSymbol, int line,
+        int col, string msg, RecognitionException e)
+    {
+        had_error = true;
+        base.SyntaxError(output, recognizer, offendingSymbol, line, col, msg, e);
+    }
+}
diff --git a/runtime/CSharp/tests/issue-3510/Program.cs b/runtime/CSharp/tests/issue-3510/Program.cs
new file mode 100644
index 0000000000..edbc54d033
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/Program.cs
@@ -0,0 +1,90 @@
+using Antlr4.Runtime;
+using System;
+using System.Linq;
+using System.Text;
+
+public class Program
+{
+    static void Main(string[] args)
+    {
+        bool show_tree = false;
+        bool show_tokens = false;
+        string file_name = null;
+        string input = null;
+        for (int i = 0; i < args.Length; ++i)
+        {
+            if (args[i].Equals("-tokens"))
+            {
+                show_tokens = true;
+                continue;
+            }
+            else if (args[i].Equals("-tree"))
+            {
+                show_tree = true;
+                continue;
+            }
+            else if (args[i].Equals("-input"))
+                input = args[i];
+            else if (args[i].Equals("-file"))
+                file_name = args[++i];
+        }
+        ICharStream str = null;
+        if (input == null && file_name == null)
+        {
+            StringBuilder sb = new StringBuilder();
+            int ch;
+            while ((ch = System.Console.Read()) != -1)
+            {
+                sb.Append((char)ch);
+            }
+            input = sb.ToString();
+            str = CharStreams.fromString(input);
+        }
+        else if (input != null)
+        {
+            str = CharStreams.fromString(input);
+        }
+        else if (file_name != null)
+        {
+            str = CharStreams.fromPath(file_name);
+        }
+        var lexer = new ChannelTestLexer(str);
+        if (show_tokens)
+        {
+            StringBuilder new_s = new StringBuilder();
+            for (int i = 0; ; ++i)
+            {
+                var ro_token = lexer.NextToken();
+                var token = (CommonToken)ro_token;
+                token.TokenIndex = i;
+                new_s.AppendLine(token.ToString());
+                if (token.Type == Antlr4.Runtime.TokenConstants.EOF)
+                    break;
+            }
+            System.Console.Error.WriteLine(new_s.ToString());
+        }
+        lexer.Reset();
+        var tokens = new CommonTokenStream(lexer);
+        var parser = new ChannelTestParser(tokens);
+        var listener_lexer = new ErrorListener<int>();
+        var listener_parser = new ErrorListener<IToken>();
+        lexer.AddErrorListener(listener_lexer);
+        parser.AddErrorListener(listener_parser);
+        parser.Profile = true;
+        var tree = parser.prog();
+        if (listener_lexer.had_error || listener_parser.had_error)
+        {
+            System.Console.Error.WriteLine("parse failed.");
+        }
+        else
+        {
+            System.Console.Error.WriteLine("parse succeeded.");
+        }
+        if (show_tree)
+        {
+            System.Console.Error.WriteLine(tree.ToStringTree());
+        }
+        System.Console.Out.WriteLine(String.Join(", ", parser.ParseInfo.getDecisionInfo().Select(d => d.ToString())));
+        System.Environment.Exit(listener_lexer.had_error || listener_parser.had_error ? 1 : 0);
+    }
+}
diff --git a/runtime/CSharp/tests/issue-3510/Test.csproj b/runtime/CSharp/tests/issue-3510/Test.csproj
new file mode 100644
index 0000000000..0065bf7594
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/Test.csproj
@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk" >
+  <PropertyGroup>
+    <TargetFramework>net5.0</TargetFramework>
+    <OutputType>Exe</OutputType>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Antlr4 Include="ChannelTest.g4" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <AntlrToolPath>../../../../tool/target/antlr4-*-SNAPSHOT-complete.jar</AntlrToolPath>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Antlr4.csproj" />
+    <PackageReference Include="Antlr4BuildTasks" Version = "8.17" PrivateAssets="all"/>
+  </ItemGroup>
+
+  <PropertyGroup>
+    <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'" >
+    <NoWarn>1701;1702;3021</NoWarn>
+  </PropertyGroup>
+</Project>
diff --git a/runtime/CSharp/tests/issue-3510/Test.sln b/runtime/CSharp/tests/issue-3510/Test.sln
new file mode 100644
index 0000000000..4768052b0f
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/Test.sln
@@ -0,0 +1,31 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.31019.35
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Test", "Test.csproj", "{FD11E8CC-1631-4FF3-9B44-F10084562311}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Antlr4", "..\..\src\Antlr4.csproj", "{A60B5000-4473-4D00-85C4-C3A4B469F608}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{FD11E8CC-1631-4FF3-9B44-F10084562311}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{FD11E8CC-1631-4FF3-9B44-F10084562311}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{FD11E8CC-1631-4FF3-9B44-F10084562311}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{FD11E8CC-1631-4FF3-9B44-F10084562311}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A60B5000-4473-4D00-85C4-C3A4B469F608}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A60B5000-4473-4D00-85C4-C3A4B469F608}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A60B5000-4473-4D00-85C4-C3A4B469F608}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A60B5000-4473-4D00-85C4-C3A4B469F608}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {2FFB66F7-2552-4F2B-B97E-77B5F8743ED4}
+	EndGlobalSection
+EndGlobal
diff --git a/runtime/CSharp/tests/issue-3510/TreeOutput.cs b/runtime/CSharp/tests/issue-3510/TreeOutput.cs
new file mode 100644
index 0000000000..def03230bb
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/TreeOutput.cs
@@ -0,0 +1,105 @@
+using Antlr4.Runtime;
+using Antlr4.Runtime.Misc;
+using Antlr4.Runtime.Tree;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+public class TreeOutput
+{
+    private static int changed = 0;
+    private static bool first_time = true;
+
+    public static StringBuilder OutputTree(IParseTree tree, Lexer lexer, Parser parser, CommonTokenStream stream)
+    {
+        changed = 0;
+        first_time = true;
+        var sb = new StringBuilder();
+        ParenthesizedAST(tree, sb, lexer, parser, stream);
+        return sb;
+    }
+
+    private static void ParenthesizedAST(IParseTree tree, StringBuilder sb, Lexer lexer, Parser parser, CommonTokenStream stream, int level = 0)
+    {
+        if (tree as TerminalNodeImpl != null)
+        {
+            TerminalNodeImpl tok = tree as TerminalNodeImpl;
+            Interval interval = tok.SourceInterval;
+            IList<IToken> inter = null;
+            if (tok.Symbol.TokenIndex >= 0)
+                inter = stream?.GetHiddenTokensToLeft(tok.Symbol.TokenIndex);
+            if (inter != null)
+                foreach (var t in inter)
+                {
+                    var ty = tok.Symbol.Type;
+                    var name = lexer.Vocabulary.GetSymbolicName(ty);
+                    StartLine(sb, level);
+                    sb.AppendLine("(" + name + " text = " + PerformEscapes(t.Text) + " " + lexer.ChannelNames[t.Channel]);
+                }
+            {
+                var ty = tok.Symbol.Type;
+                var name = lexer.Vocabulary.GetSymbolicName(ty);
+                StartLine(sb, level);
+                sb.AppendLine("( " + name + " i =" + tree.SourceInterval.a
+                    + " txt =" + PerformEscapes(tree.GetText())
+                    + " tt =" + tok.Symbol.Type
+                    + " " + lexer.ChannelNames[tok.Symbol.Channel]);
+            }
+        }
+        else
+        {
+            var x = tree as RuleContext;
+            var ri = x.RuleIndex;
+            var name = parser.RuleNames[ri];
+            StartLine(sb, level);
+            sb.Append("( " + name);
+            sb.AppendLine();
+        }
+        for (int i = 0; i<tree.ChildCount; ++i)
+        {
+            var c = tree.GetChild(i);
+            ParenthesizedAST(c, sb, lexer, parser, stream, level + 1);
+        }
+        if (level == 0)
+        {
+            for (int k = 0; k < 1 + changed - level; ++k) sb.Append(") ");
+            sb.AppendLine();
+            changed = 0;
+        }
+    }
+
+    private static void StartLine(StringBuilder sb, int level = 0)
+    {
+        if (changed - level >= 0)
+        {
+            if (!first_time)
+            {
+                for (int j = 0; j < level; ++j) sb.Append("  ");
+                for (int k = 0; k < 1 + changed - level; ++k) sb.Append(") ");
+                sb.AppendLine();
+            }
+            changed = 0;
+            first_time = false;
+        }
+        changed = level;
+        for (int j = 0; j < level; ++j) sb.Append("  ");
+    }
+
+    private static string ToLiteral(string input)
+    {
+        using (var writer = new StringWriter())
+        {
+            var literal = input;
+            literal = literal.Replace("\\", "\\\\");
+            return literal;
+        }
+    }
+
+    public static string PerformEscapes(string s)
+    {
+        StringBuilder new_s = new StringBuilder();
+        new_s.Append(ToLiteral(s));
+        return new_s.ToString();
+    }
+}
diff --git a/runtime/CSharp/tests/issue-3510/input.txt b/runtime/CSharp/tests/issue-3510/input.txt
new file mode 100644
index 0000000000..55c21ae456
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/input.txt
@@ -0,0 +1 @@
+111 222 aaa 333 BBB 444
diff --git a/runtime/CSharp/tests/issue-3510/test.sh b/runtime/CSharp/tests/issue-3510/test.sh
new file mode 100644
index 0000000000..d08f147e4f
--- /dev/null
+++ b/runtime/CSharp/tests/issue-3510/test.sh
@@ -0,0 +1,11 @@
+#!/usr/bin/bash
+
+dotnet restore
+dotnet build
+dotnet run -file input.txt
+if [[ "$?" != "0" ]]
+then
+    echo "Issue 3510 test failed."
+    exit 1
+fi
+
diff --git a/tool/resources/org/antlr/v4/tool/templates/codegen/CSharp/CSharp.stg b/tool/resources/org/antlr/v4/tool/templates/codegen/CSharp/CSharp.stg
index 5bc87079b0..ba7db09a4a 100644
--- a/tool/resources/org/antlr/v4/tool/templates/codegen/CSharp/CSharp.stg
+++ b/tool/resources/org/antlr/v4/tool/templates/codegen/CSharp/CSharp.stg
@@ -762,9 +762,9 @@ LexerSkipCommand()  ::= "Skip();"
 LexerMoreCommand()  ::= "More();"
 LexerPopModeCommand() ::= "PopMode();"
 
-LexerTypeCommand(arg, grammar)      ::= "_type = <tokenType.(arg)>;"
-LexerChannelCommand(arg, grammar)   ::= "_channel = <channelName.(arg)>;"
-LexerModeCommand(arg, grammar)      ::= "_mode = <modeName.(arg)>;"
+LexerTypeCommand(arg, grammar)      ::= "Type = <tokenType.(arg)>;"
+LexerChannelCommand(arg, grammar)   ::= "Channel = <channelName.(arg)>;"
+LexerModeCommand(arg, grammar)      ::= "CurrentMode = <modeName.(arg)>;"
 LexerPushModeCommand(arg, grammar)  ::= "PushMode(<modeName.(arg)>);"
 
 ActionText(t) ::= "<t.text>"