OData reader fails to read payloads having lowercase EDM types about odata.net

[habbes]

@budt12 Since some concerns have been raised about the currently open PR, and discussions are ongoing, I want to suggest a workaround in the meantime. The workaround consists of providing a custom type resolver delegate to the ODataMessageWriterSettings.ClientCustomTypeResolver property. The custom resolver can then implement custom logic to handle types that are not found in your model using the default (case-sensitive) IEdmModel.FindType extension method.

Here's a sample implementation of such a custom resolver. It builds a static case-insensitive copy of the core schema types in the EdmCoreModel. When a type is not found, it looks it up in this cache. Building the cache is a one-time cost. I opted to copy only the core model types in order to keep the cache small and because your use-case seems to be concerned only with EDM primitve types.

private static Dictionary<string, IEdmType> caseInsensitiveCoreTypesCache = BuildCaseInsensitiveCoreTypesCache();

public static IEdmType ResolveType(IEdmType expectedType, string typeName)
{
      IEdmType resolvedType = MyModel.FindType(typeName);
      if (resolvedType == null)
      {
            var qualifiedTypeName = typeName.Contains(".") ? typeName : $"Edm.{typeName}";
            caseInsensitiveCoreTypeCache.TryGetValue(qualifiedTypeName, out resolvedType);
      }

      return resolvedType;
}

private static Dictionary<string, IEdmType> BuildCaseInsensitiveCoreTypesCache()
{
    var cache = new Dictionary<string, IEdmType>(StringComparer.OrdinalIgnoreCase);
    foreach (var type in EdmCoreModel.Instance.SchemaElements)
    {
        cache.Add(type.FullName(), type as IEdmType);
    }

    return cache;
}

And here's how you would pass it to the reader settings:

messageReaderSettings.ClientCustomTypeResolver = ResolveType

[corranrogue9]

Let's see if we can parameterize the comparer and run benchmarks at a later time. We will need to benchmark if we can't parameterize the comparer for some reason.