Check if a type is a keyword before using short names.

XmlSchemaClassGenerator/CodeUtilities.cs

@@ -1,4 +1,6 @@
-using System;
+using Microsoft.CSharp;
+
+using System;
 using System.CodeDom;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -172,7 +174,7 @@ public static string GetUniqueFieldName(this TypeModel typeModel, PropertyModel
  var classModel = typeModel as ClassModel;
  var propBackingFieldName = propertyModel.Name.ToBackingField(classModel?.Configuration.PrivateMemberPrefix);
 
- if (!IsValidIdentifier(propBackingFieldName.ToLower()))
+ if (!CSharp.IsValidIdentifier(propBackingFieldName.ToLower()))
  propBackingFieldName = "@" + propBackingFieldName;
 
  if (classModel == null)
@@ -214,7 +216,7 @@ public static string GetUniquePropertyName(this TypeModel tm, string name)
 
  internal static string NormalizeNewlines(string text) => NormalizeNewlinesRegex.Replace(text, "$1\r\n");
 
- private static readonly Predicate<string> IsValidIdentifier = new Microsoft.CSharp.CSharpCodeProvider().IsValidIdentifier;
+ private static readonly CSharpCodeProvider CSharp = new();
 
  internal static Uri CreateUri(string uri) => string.IsNullOrEmpty(uri) ? null : new Uri(uri);
 
@@ -255,7 +257,9 @@ public static bool IsUsingNamespace(string namespaceName, GeneratorConfiguration
 
  public static CodeTypeReference CreateTypeReference(Type type, GeneratorConfiguration conf)
  {
- if (IsUsingNamespace(type.Namespace, conf))
+ // If the type is a keyword it will prefix it with an underscore to make it a valid identifier.
+ var isKeyword = CSharp.CreateValidIdentifier(CSharp.GetTypeOutput(new(type)))[0] == '_';
+ if (!isKeyword && IsUsingNamespace(type.Namespace, conf))
  {
  var typeRef = new CodeTypeReference(type.Name, conf.CodeTypeReferenceOptions);