ASP.Net MVC ModelBindingContext class— how are its model values populated?

Question

I\'m scratching my head a bit at how model binders do their work in ASP.Net MVC.

To be specific, the BindModel() method has a ModelBindingContext parameter that ho

Answer 1

The ModelBindingContext "knows" the type of model it's being handed because you have to either:

• Add a ModelBinder attribute to your model
• Register the ModelBinder with your model using the ModelBinders.Binders.Add() method.

Example of ModelBinder attribute:

[ModelBinder(typeof(ContactBinder))]
public class Contact { ... }

Example of ModelBinders.Binders.Add():

void Application_Start()
{
  ModelBinders.Binders[typeof(Contact)] = new ContactBinder();
}

If you have registered your ModelBinder and have implemented the BindModel method:

public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) { ... }

1. Query the ModelBindingContext.ModelType is equal to your Model e.g.

   if (bindingContext.ModelType == typeof(Contact)) { ... }
   

2. Rehydrate your model from the ModelBindingContext.ValueProvider property to retrieve ValueProviderResult instances that represent the data from form posts, route data, and the query string e.g.

   bindingContext.ValueProvider["Name"].AttemptedValue;
   

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