Don't use C# name in model dictionary (#5376)

* Don't use C# name in model dictionary

* Same for visitedTypes

* Update generated code

* Update preview.yml

* Update preview.yml

* Update preview.yml

* Update eng/pipelines/preview.yml

---------

Co-authored-by: JoshLove-msft <[email protected]>
Co-authored-by: Wei Hu <[email protected]>

Author: 3 people

src/AutoRest.CSharp/Common/Generation/Writers/ModelReaderWriterContextWriter.cs

@@ -80,15 +80,15 @@ private static bool IsObsolete(CSharpType type)
         private IEnumerable<CSharpType> CollectBuildableTypes(IEnumerable<TypeProvider> models)
         {
             var buildableTypes = new HashSet<CSharpType>(new CSharpTypeNameComparer());
-            var visitedTypes = new HashSet<CSharpType>(new CSharpTypeNameComparer());
+            var visitedTypes = new HashSet<CSharpType>();
 
             // for all Resource types, just add them directly to buildableTypes
             foreach (var resource in models.OfType<Resource>())
             {
                 buildableTypes.Add(resource.Type);
             }
 
-            var modelDictionary = models.OfType<SerializableObjectType>().ToDictionary(m => m.Type, m => m, new CSharpTypeNameComparer());
+            var modelDictionary = models.OfType<SerializableObjectType>().ToDictionary(m => m.Type, m => m);
 
             foreach (var model in modelDictionary.Values)
             {

test/TestProjects/Customizations-TypeSpec/src/Generated/Models/CustomizationsInTspContext.cs

@@ -14,7 +14,7 @@ namespace CustomizationsInTsp
     /// Context class which will be filled in by the System.ClientModel.SourceGeneration.
     /// For more information see 'https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/core/System.ClientModel/src/docs/ModelReaderWriterContext.md'
     /// </summary>
-    [ModelReaderWriterBuildable(typeof(ModelStruct?))]
+    [ModelReaderWriterBuildable(typeof(ModelStruct))]
     [ModelReaderWriterBuildable(typeof(ModelToAddAdditionalSerializableProperty))]
     [ModelReaderWriterBuildable(typeof(ModelToChangeNamespace))]
     [ModelReaderWriterBuildable(typeof(ModelToMakeInternal))]