“This property setter is obsolete, because its value is derived from ModelMetadata.Model now.”

Question

http://www.asp.net/learn/mvc/tutorial-39-cs.aspx

We are using the above guide to implement some validation in our ASP.NET MVC app.

We receive the following e

Answer 1

You will get this error when you create a new ModelBindingContext and then attempt to set the ModelType property, in MVC 2 preview 2 or higher. For example, in a unit test for a custom model binder in older versions of MVC, I had code like the following:

    internal static T Bind<T>(string prefix, FormCollection collection, ModelStateDictionary modelState) where T:class
    {
        var mbc = new ModelBindingContext()
        {
            ModelName = prefix,
            ModelState = modelState,
            ModelType = typeof(T),
            ValueProvider = collection.ToValueProvider()
        };
        IModelBinder binder = new MyModelBinder();
        var cc = new ControllerContext();
        return binder.BindModel(cc, mbc) as T;
    }

When I updated to MVC 2 preview 2, I got the same error as you described. The fix was to change this code to this:

    internal static T Bind<T>(string prefix, FormCollection collection, ModelStateDictionary modelState) where T:class
    {
        var mbc = new ModelBindingContext()
        {
            ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, typeof(T)),
            ModelName = prefix,
            ModelState = modelState,
            ValueProvider = collection.ToValueProvider()
        };
        IModelBinder binder = new MyModelBinder();
        var cc = new ControllerContext();
        return binder.BindModel(cc, mbc) as T;
    }

Note that I have removed the assignment of ModelType, and replaced it with an assignment to ModelMetadata. Visual Studio should tell you which line of code is actually throwing this error.