Question

I consume an API that has a full object set. I don’t want to have to re-create an object model in the mvc3 code just to use the DataAnnotations.

Is there a way to use this feature with out a wrapper class? The objects have their own validation rules that I can reuse, but want to use the built in mvc framework to display the messages back.

Answer 1

You can create a class which inherits from DataAnnotationsModelMetadataProvider, where you can consume your object set, and write out the items as DataAnnotations. A brief example:

public class MyModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    private MyEntities _db = new MyEntities();

    protected override ModelMetadata CreateMetadata(
        IEnumerable<Attribute> attributes, 
        Type containerType, 
        Func<object> modelAccessor, 
        Type modelType, 
        string propertyName)
    {
        var modelMetadata = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);

        // load object
        var objectSet = _db.ObjectSets.FirstOrDefault(x => x.PropertyName == propertyName);

        // check attributes
        if (objectSet.IsRequired)
            modelMetadata.IsRequired = true;

        return modelMetadata;
    }
}

Then, register your provider in Global.asax.cs in the Application_Start method, as follows:

        ModelMetadataProviders.Current = new MyModelMetadataProvider();