Auto-binding an "XElement" property in ASP.NET MVC

Question

I have an "Edit" action and an "Edit" view to allow users to update a certain entity in the database.

It's database type is "XML", and the DataContext (I'm using Linq-to-SQL) represents it as a property of type "XElement".

In my view, I render a text-area from the "ToString()" output of the propery like this:

<%= Html.TextArea("Text", Model.Text.ToString()) %>

This works fine when pulling the data from the object, but when I try to post the new data back, it comes back as blank.

I think this is because the auto-binder doesn't know how to deal with a property of type XElement.

Is there a way to fix this, or to somehow customize the behavior of the auto-binder so that it de-serializes the incoming data properly?

Answer 1

You can write a custom binder for this that implements the IModelBinder interface. You can register this binder on the method itself:

public ActionResult Edit([ModelBinder(typeof(XElementBinder))] XElement element)
{ ... }

or globally for all XElement's in your application by registereing your binder in Global.asax:

ModelBinders.Binders[typeof(IPrincipal)] = new PrincipalModelBinder();

Your custom binder would look something like this:

public class XElementModelBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext,
                            ModelBindingContext bindingContext)
    {
        string text = controllerContext.HttpContext.Request.Form["Text"];
        XElement element = ...;
        // Get XElement instance from posted data.
        return element;
    }
}