ASP.NET MVC null ViewResult

Question

How should one deal with an MVC controller returning a null ViewResult?

As an example I am creating a simple edit view:

    public ActionResult Edit(int id)
    {
        var person = (from p in context.SWLiftShare_Persons
                      where p.id == id
                      select p).SingleOrDefault();

        if (person != null)
        {
            return View(person);
        }
        else return View();
    }

I guess in reality there's no point in checking for a null result in the controller because the view picks out properties from the model:

<h2>Edit - <%= Html.Encode(Model.Name) %></h2>

<%= Html.ValidationSummary("Edit was unsuccessful. Please correct the errors and try again.") %>

<% using (Html.BeginForm()) {%>

    <fieldset>
        <legend>Fields</legend>
        <p>
            <label for="id">id:
            <%= Html.Encode(Model.id) %></label>
        </p>
        <p>
            <label for="CollarNumber">CollarNumber:</label>
            <%= Html.TextBox("CollarNumber", Model.CollarNumber)%>
            <%= Html.ValidationMessage("CollarNumber", "*") %>
        </p>
        <p>
            <label for="Name">Name:</label>
            <%= Html.TextBox("Name", Model.Name)%>
            <%= Html.ValidationMessage("Name", "*") %>
        </p>
        <p>
            <label for="EmailAddress">EmailAddress:</label>
            <%= Html.TextBox("EmailAddress", Model.EmailAddress, new { style = "width:300px" })%>
            <%= Html.ValidationMessage("EmailAddress", "*") %>
        </p>
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
<% } %>

I could just wrap everything in a <% if(Model != null) { //render edit markup... etc. but that seems rather unelegant. Is there a better way to deal with this?

Jan Willem B · Accepted Answer · 2010-05-11 08:56:07Z

2

In this case it seems to be an error if person becomes null. You could render a different (error) view if this is the case. For example:

if (person == null) 
{
  return View("ErrorView");
}

return View(person);

ErrorView.aspx:

<div>Person was not found. Try again.</div>

answered May 11, 2010 at 8:56

Jan Willem B

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Comments

James H · Accepted Answer · 2010-05-11 09:02:03Z

1

In this scenario, I would return another view when the person is null to cleanly separate your view logic:

public ActionResult Edit(int id)  
{  
    var person = (from p in context.SWLiftShare_Persons  
                  where p.id == id  
                  select p).SingleOrDefault();  

    return (person != null) ? View(person) : View("InvalidPerson");
}

answered May 11, 2010 at 9:02

James H

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Comments

takepara · Accepted Answer · 2010-05-13 00:58:50Z

0

I think...

throw new HttpException(404,"Not found");

and set custom errors.

answered May 13, 2010 at 0:58

takepara

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