"Simple.OData.Client.UnresolvableObjectException: Type [FooStatus] not found" for Enum Foo

[iant-ee]

I've come across some odd behaviour which is as much about our specific OData setup as it is a problem in the library, but I just wanted to note it here for our future reference and for the benefit of anyone searching for this error message.

Our client has a simple search using a c# Enum:

namespace Enums
{
    public enum FooStatus
    {
        Published = 1,
        Draft = 2,
        Deleted = 3
    }
}

var publishedFoos = await client
    .For<Foo>()
    .Filter(f => f.FooStatus.ToString() == Enums.FooStatus.Published);
    .FindEntriesAsync();

This results in the following error:

Simple.OData.Client.UnresolvableObjectException: Type [FooStatus] not found
   at Simple.OData.Client.V4.Adapter.Metadata.GetQualifiedTypeName(String typeName)
   at Simple.OData.Client.Adapter.MetadataCache.<GetQualifiedTypeName>b__37_0(String x)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Simple.OData.Client.Adapter.MetadataCache.GetQualifiedTypeName(String typeOrCollectionName)
   at Simple.OData.Client.V4.Adapter.CommandFormatter.ConvertValueToUriLiteral(Object value, Boolean escapeDataString)
   at Simple.OData.Client.ODataExpression.FormatValue(ExpressionContext context)
   at Simple.OData.Client.ODataExpression.FormatToStringFunction(ExpressionContext context)
   at Simple.OData.Client.ODataExpression.FormatFunction(ExpressionContext context)
   at Simple.OData.Client.ODataExpression.Format(ExpressionContext context)
   at Simple.OData.Client.ODataExpression.FormatExpression(ODataExpression expr, ExpressionContext context)
   at Simple.OData.Client.ODataExpression.Format(ExpressionContext context)
   at Simple.OData.Client.ResolvedCommand.ResolveFilter(FluentCommandDetails details)
   at Simple.OData.Client.ResolvedCommand..ctor(FluentCommand command, ISession session)
   at Simple.OData.Client.FluentCommand.Resolve(ISession session)
   at Simple.OData.Client.BoundClient`1.FindEntriesAsync(ODataFeedAnnotations annotations, CancellationToken cancellationToken)

Digging into this I've discovered that because we're using a C# Enum in our client code, the library assumes that we've also got an Enums in our OData service. In fact the OData service we're calling defines this column as a string, so in the example above we'd want the filter to be FooStatus eq "Published".

<EntityType Name="Foo">
<Key>
<PropertyRef Name="FooId"/>
</Key>
<Property Name="DisplayName" Type="Edm.String"/>
<Property Name="FooStatus" Type="Edm.String"/>
</EntityType>

The relevant library code is:

public class CommandFormatter : CommandFormatterBase
{
    public override string ConvertValueToUriLiteral(object value, bool escapeDataString)
    {
        var type = value?.GetType();

        if (value != null && _session.TypeCache.IsEnumType(type))
        {
            value = new ODataEnumValue(value.ToString(), _session.Metadata.GetQualifiedTypeName(type.Name));
        }
        ...
    }
}

IsEnumType checks if we have a c# enum.
Metadata.GetQualifiedTypeName looks up the name of the OData Enum.

Fix for us will be to use a string in our client code, instead of the c# enum.