Null reference error in asp.net MVC3

Question

I am using following line in my asp.net MVC 3 view.

@Model.AuthorizedAgent.Person.FirstName

But I am getting error because AuthorizedAgent is null. How can I avoid this error ?

Easy, make sure AuthorizedAgent is not null. For any more help than that you're going to need to show us more code. :) — Talljoe
– Talljoe, Commented Apr 26, 2011 at 14:52
What If I want to provide alternate text if some value is null ? — DotnetSparrow
– DotnetSparrow, Commented Apr 26, 2011 at 14:58
I would create a viewmodel with a property named firstname and then set the property in the controller according if the value is null or not to avoid putting logic in your view. — ryudice
– ryudice, Commented Apr 26, 2011 at 15:02

Darin Dimitrov · Accepted Answer · 2011-04-26 15:05:43Z

1

You could use a view model with the following property:

@Html.DisplayFor(x => x.AuthorizedAgentFirstName)

and then have the controller perform the necessary tests and populate the property accordingly:

public ActionResult Foo()
{
    SomeModel model = ...
    SomeViewModel vm = new SomeViewModel();

    // TODO: refactor this part to a mapping layer. AutoMapper is 
    // a good tool for the job
    if (model.AuthorizedAgent != null && model.AuthorizedAgent.Person != null)
    {
        vm.AuthorizedAgentFirstName = model.AuthorizedAgent.Person.FirstName;
    }
    return View(vm);
}

And in order to provide an alternate text of the value is null you could use the DisplayFormat attribute:

[DisplayFormat(NullDisplayText = "EMPTY")]
public string AuthorizedAgentFirstName { get; set; }

answered Apr 26, 2011 at 15:05

Darin Dimitrov

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Comments

Gregory A Beamer · Accepted Answer · 2011-04-26 14:57:45Z

0

You have two options here. The first is to ensure the model has a value. Without seeing your code, I have no clue whether this should always have a value or not. The other option is conditionally grabbing the value, which you can do easily in both ASP.NET and Razor view engines.

answered Apr 26, 2011 at 14:57

Gregory A Beamer

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