Binding Data to an Existing Object in Asp.net MVC

Question

Within an ASP.Net MVC model binder is it possible to create an object of the bound type and then update the properties on it.

e.g.

public override object BindModel(ControllerContext controllerContext,
    ModelBindingContext bindingContext)
{
    ParentType boundModel = null;
    if (bindingContext.ModelType == typeof(ParentType))
    {
        var myFactory = new MyFactory();
        var someValue = bindingContext.ValueProvider.GetValue
            ("someFieldId").AttemptedValue;
        ChildType child = myFactory.Create(someValue);
        BindModel(child);
        boundModel = child;
    }
    return boundModel;
}

In this code I want to know if there is something similar to the BindModel(child) call, kind of like TryModelUpdate() from a controller?

I have two child classes and which one is instantiated is based on a drop down list with id "someFieldId". So I would like to instantiate the Child class using the factory then update all the Parent properties from the form using a TryUpdateModel / BindModel call. I would then like the bound model passed to the controller. — Russell Giddings
– Russell Giddings, Commented Feb 19, 2010 at 17:49

Robert Harvey · Accepted Answer · 2010-02-19 21:22:50Z

2

I think a better approach to your problem would be to derive from the DefaultModelBinder (which I think you probably are) and then override the CreateModel method rather than the BindModel method.

By returning your Child object from that, you should be along the path you're looking for.

edited Feb 19, 2010 at 21:22

Robert Harvey

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answered Feb 19, 2010 at 19:29

Paul

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1 Comment

Russell Giddings Over a year ago

This looks like a perfect solution. I'll give it a try and get back to you :-)

takepara · Accepted Answer · 2010-02-21 15:56:11Z

0

public override object BindModel(ControllerContext controllerContext, 
                                 ModelBindingContext bindingContext)
{
    ParentType boundModel = null;
    if (bindingContext.ModelType == typeof(ParentType))
    {
        var myFactory = new MyFactory();
        var someValue = bindingContext.ValueProvider
                                      .GetValue("someFieldId").AttemptedValue;
        ChildType child = myFactory.Create(someValue);
        BindModel(child);
        boundModel = child;
    }

    // change here
    bindingContext.ModelMetadata.Model = boundModel;
    return BindModel(controllerContext, bindingContext);
}

How about this?

answered Feb 21, 2010 at 15:56

takepara

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1 Comment

Russell Giddings Over a year ago

Unfortunately the method 'BindModel(child)' doesn't exist. That was the issue with my example code. :-(

Simon Thompson · Accepted Answer · 2010-11-18 10:59:59Z

0

The binder simply need the same names in class properties and the field value, calling updatemodel will place any matching values into the model.

So you should be able to just create either type of class and call updatemodel ???

answered Nov 18, 2010 at 10:59

Simon Thompson

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