Passing a model property to a partial view

Question

I'm having trouble passing the correct data to a partial view, and I'm not sure why it is failing.

Say I have models

public class SubModel {
  public string Wobble {get; set;}
}

public class MyModel {
  public SubModel Wibble {get; set;}
}

and views

MyView.cshtml

@model MyModel

@Html.Partial("SomePartial", Model.Wibble)

and

SomePartial.cshtml

@model SubModel

<h1>Victory!</h1>

this fails with The model item passed into the dictionary is of type 'MyModel', but this dictionary requires a model item of type 'MySubModel'

When I change MyView.cshtml to

@model MyModel

@Html.Partial("SomePartial", Model.Wibble, new ViewDataDictionary<MySubModel>(Model.Wibble))

It works as expected.

Why do I need to explicitly pass a ViewDataDictionary? Why can't I just pass the model?

Note: I'm using a library that does things that make me go hrm? a lot of the time. If the above behaviour is not expected, it might be this libraries fault.

Answer 1

This happens when the model you pass to the partial view is null. Don't pass null to a partial view, or it will get confused about its type.