当value为null时，将nullable boolean传递给部分视图不起作用

Question

I'm trying to do this in my razor view:

@{ Html.RenderPartial("_Checkbox", Model.SomeNullableBoolean); }

_Checkbox.cshtml:

@model bool?

@if (Model == null)
{
    Some code
}
else if (Model == true)
{
    Some other code
}

This works fine as long as the Model.SomeNullableBoolean is set to either true or false . But if the value is null I get the following error:

The model item passed into the dictionary is of type 'System.Data.Entity.DynamicProxies.MyAwesomeModel_EB6A12E11ECADA2C6B22289ACDF73813854383896F2E78956FDFFE6225F0404F', but this dictionary requires a model item of type 'System.Nullable`1[System.Boolean]'.

The nullable property inside the model ( MyAwesomeModel ) is defined like this:

public bool? SomeNullableBoolean { get; set; }

Any ideas how I should investigate this further?

Answer 1

I followed Stephen Muecke's advice and went with the ViewDataDictionary approach:

@{ Html.RenderPartial("_Checkbox", null, new ViewDataDictionary { { "BoolValue", Model.SomeNullableBoolean}}); }

_Checkbox.cshtml:

@{
    var theValue = (bool?) ViewData["BoolValue"];
}

@if (theValue == null)
{
    something
}
else if (theValue == true)
{
    something
}
else
{
    something
}

This works perfectly!

Answer 2

When you pass a model to a partial which is null , by default it will use the model in the main view, so in your case its passing and instance of MyAwesomeModel to a view that expects a model which is bool? (hence the error).

You need to conditionally pass a new ViewDataDictionary if the value of the property is null

@{ Html.RenderPartial("_Checkbox", Model.SomeNullableBoolean.HasValue ?
    new ViewDataDictionary(){ Model = Model.SomeNullableBoolean } : 
    new ViewDataDictionary()); }