如何实例化CachedDataAnnotationsModelMetadata？

Question

I'm trying to test a custom model binder. As part of that process I am creating a new ModelBindingContext to pass into the BindModel method of the custom binder. The problem is that I need to set the MetaData property of the ModelBindingContext as a CachedDataAnnotationsModelMetadata object, but honestly am not sure how to instantiate the object.

The signature for the CachedDataAnnotationsModelMetadata object is:

public CachedDataAnnotationsModelMetadata( CachedDataAnnotationsModelMetadata prototype, Func<object> modelAccessor )

Does anyone have an example of what the prototype and modelAccessor parameters are supposed to be?

Here's a snippet of the non-functional code.

        // Assemble
        var formCollection = new List<KeyValuePair<string, string>> {
            new KeyValuePair<string, string> ("SomeRequiredProperty", "SomeValue")
        };

        var valueProvider = new System.Web.Http.ValueProviders.Providers.NameValuePairsValueProvider(formCollection, null);

        var metadata = new System.Web.Http.Metadata.Providers.CachedDataAnnotationsModelMetadata(????, ????)

        var bindingContext = new ModelBindingContext {
            ModelName = "ClaimsModelBinderInputModel",
            ValueProvider = valueProvider,
            ModelMetadata = metadata
        };
        var actionContext = new HttpActionContext();

        var httpControllerContext = new HttpControllerContext();
        httpControllerContext.Request = new HttpRequestMessage(HttpMethod.Post, "http://localhost/someUri");
        actionContext.ControllerContext = httpControllerContext;

        var cmb = new ClaimsModelBinder();

        // Act
        cmb.BindModel(actionContext, bindingContext);
        // Assert...

I've found a few examples around the net and SO of people interacting with this class, but no concrete example of implementing it.

Thanks in advance!

Update

Figured out ModelAccessor , it's just used to delay accessing the actual model until the model property is accessed. https://github.com/ASP-NET-MVC/aspnetwebstack/blob/master/src/System.Web.Http/Metadata/ModelMetadata.cs#L103

I'm still working on supplying a prototype object if anyone can help with that.

Answer 1

So I ended up sidestepping this issue entirely.

After inspecting the inheritance model, I realized that in this case I can get away with using the DataAnnotationsModelMetadataProvider rather than the CachedDataAnnotationsModelMetadata . The latter of these doesn't require the parameters necessary to setup caching, and since I don't need caching to test what I am testing, the standard DataAnnotationsModelMetadataProvider will suffice.

I was able to identify that I could take a different approach after reading through the source code for the metadata namespace.

https://github.com/ASP-NET-MVC/aspnetwebstack/tree/master/src/System.Web.Http/Metadata

That said, if anyone else can provide some clues to my original question, I would prefer to use the cached model object if possible.