Do not allow GetType and compare ignoring case

src/Build.UnitTests/Evaluation/Expander_Tests.cs

@@ -4978,6 +4978,56 @@ public void ExpandItem_ConvertToStringUsingInvariantCultureForNumberData_Respect
             }
         }
 
+        [Theory]
+        [InlineData("getType")]
+        [InlineData("GetType")]
+        [InlineData("gettype")]
+        public void GetTypeMethod_ShouldNotBeAllowed(string methodName)
+        {
+            using (var env = TestEnvironment.Create())
+            {
+                var root = env.CreateFolder();
+
+                var projectFile = env.CreateFile(root, ".proj",
+                    @$"<Project>
+    <PropertyGroup>
+        <foo>aa</foo>
+        <typeval>$(foo.{methodName}().FullName)</typeval>
+    </PropertyGroup>
+</Project>");
+                var exception = Should.Throw<InvalidProjectFileException>(() =>
+                {
+                    new ProjectInstance(projectFile.Path);
+                });
+                exception.BaseMessage.ShouldContain($"The function \"{methodName}\" on type \"System.String\" is not available for execution as an MSBuild property function.");
+            }
+        }
+
+        [Theory]
+        [InlineData("getType")]
+        [InlineData("GetType")]
+        [InlineData("gettype")]
+        public void GetTypeMethod_ShouldBeAllowed_EnabledByEnvVariable(string methodName)
+        {
+            using (var env = TestEnvironment.Create())
+            {
+                env.SetEnvironmentVariable("MSBUILDENABLEALLPROPERTYFUNCTIONS", "1");
+                var root = env.CreateFolder();
+
+                var projectFile = env.CreateFile(root, ".proj",
+                    @$"<Project>
+    <PropertyGroup>
+        <foo>aa</foo>
+        <typeval>$(foo.{methodName}().FullName)</typeval>
+    </PropertyGroup>
+</Project>");
+                Should.NotThrow(() =>
+                {
+                    new ProjectInstance(projectFile.Path);
+                });
+            }
+        }
+
         /// <summary>
         /// Determines if ICU mode is enabled.
         /// Copied from: https://learn.microsoft.com/en-us/dotnet/core/extensions/globalization-icu#determine-if-your-app-is-using-icu

src/Build/Evaluation/Expander.cs

@@ -5308,7 +5308,7 @@ private static bool IsInstanceMethodAvailable(string methodName)
                 }
 
                 // This could be expanded to an allow / deny list.
-                return methodName != "GetType";
+                return !string.Equals("GetType", methodName, StringComparison.OrdinalIgnoreCase);
             }
 
             /// <summary>