public override IModelBinder GetBinder(ModelBindingExecutionContext modelBindingExecutionContext, ModelBindingContext bindingContext)
{
ModelBinderUtil.ValidateBindingContext(bindingContext);
Type[] typeArguments = null;
if (ModelType.IsInterface)
{
Type matchingClosedInterface = TypeHelpers.ExtractGenericInterface(bindingContext.ModelType, ModelType);
if (matchingClosedInterface != null)
{
typeArguments = matchingClosedInterface.GetGenericArguments();
}
}
else
{
typeArguments = TypeHelpers.GetTypeArgumentsIfMatch(bindingContext.ModelType, ModelType);
}
if (typeArguments != null)
{
if (SuppressPrefixCheck || bindingContext.UnvalidatedValueProvider.ContainsPrefix(bindingContext.ModelName))
{
return(_modelBinderFactory(typeArguments));
}
}
return(null);
}
// Returns the generic type arguments for the model type if updatable, else null.
// supportedInterfaceType: open type (like IList<>) of supported interface, must implement ICollection<>
// newInstanceType: open type (like List<>) of object that will be created, must implement supportedInterfaceType
public static Type[] GetTypeArgumentsForUpdatableGenericCollection(Type supportedInterfaceType, Type newInstanceType, ModelMetadata modelMetadata)
{
/*
* Check that we can extract proper type arguments from the model.
*/
if (!modelMetadata.ModelType.IsGenericType || modelMetadata.ModelType.IsGenericTypeDefinition)
{
// not a closed generic type
return(null);
}
Type[] modelTypeArguments = modelMetadata.ModelType.GetGenericArguments();
if (modelTypeArguments.Length != supportedInterfaceType.GetGenericArguments().Length)
{
// wrong number of generic type arguments
return(null);
}
/*
* Is it possible just to change the reference rather than update the collection in-place?
*/
if (!modelMetadata.IsReadOnly)
{
Type closedNewInstanceType = newInstanceType.MakeGenericType(modelTypeArguments);
if (modelMetadata.ModelType.IsAssignableFrom(closedNewInstanceType))
{
return(modelTypeArguments);
}
}
/*
* At this point, we know we can't change the reference, so we need to verify that
* the model instance can be updated in-place.
*/
Type closedSupportedInterfaceType = supportedInterfaceType.MakeGenericType(modelTypeArguments);
if (!closedSupportedInterfaceType.IsInstanceOfType(modelMetadata.Model))
{
return(null); // not instance of correct interface
}
Type closedCollectionType = TypeHelpers.ExtractGenericInterface(closedSupportedInterfaceType, typeof(ICollection <>));
bool collectionInstanceIsReadOnly = (bool)closedCollectionType.GetProperty("IsReadOnly").GetValue(modelMetadata.Model, null);
if (collectionInstanceIsReadOnly)
{
return(null);
}
else
{
return(modelTypeArguments);
}
}