asp.net mvc - Custom Model Binder for Complex composite objects HELP

Question

I am trying to write a custom model binder but I'm having great difficulty trying to figure how to bind complex composite objects.

this is the class I'm trying to bind to:

public class Fund
{
        public int Id { get; set; }
        public string Name { get; set; }
        public List<FundAllocation> FundAllocations { get; set; }
}

and this is how my attempt at writing the custom binder looks like:

public class FundModelBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        throw new NotImplementedException();
    }

    public object GetValue(ControllerContext controllerContext, string modelName, Type modelType, ModelStateDictionary modelState)
    {
        var fund = new Fund();

        fund.Id = int.Parse(controllerContext.HttpContext.Request.Form["Id"]);
        fund.Name = controllerContext.HttpContext.Request.Form["Name"];

        //i don't know how to bind to the list property :(
        fund.FundItems[0].Catalogue.Id = controllerContext.HttpContext.Request.Form["FundItem.Catalogue.Id"];
        return fund;
    }
}

Any Ideas

thanks Tony

Answer 1

Do you really need to implement a custom ModelBinder here? The default binder may do what you need (as it can populate collections and complex objects):

Lets say your controller action looks like this:

public ActionResult SomeAction(Fund fund)
{
  //do some stuff
  return View();
}

And you html contains this:

<input type="text" name="fund.Id" value="1" />
<input type="text" name="fund.Name" value="SomeName" />

<input type="text" name="fund.FundAllocations.Index" value="0" />
<input type="text" name="fund.FundAllocations[0].SomeProperty" value="abc" />

<input type="text" name="fund.FundAllocations.Index" value="1" />
<input type="text" name="fund.FundAllocations[1].SomeProperty" value="xyz" />

The default model binder should initialise your fund object with 2 items in the FundAllocations List (I don't know what your FundAllocation class looks like, so I made up a single property "SomeProperty"). Just be sure to include those "fund.FundAllocations.Index" elements (which the default binder looks at for it's own use), that got me when I tried to get this working).