fix System.NullReferenceException in C#

Question

i m developing a website and stuck with System.NullReferenceException . on the master page I m using this code

if (Request.Url.ToString().ToLower().Contains("content.aspx"))
{
    if (Request.Params["ModuleID"].ToString() == null)
    {
        Response.Redirect("Content.aspx?ModuleID=1");
    }
}

when Module Id is blank then it creates null reference exception.

You already said where the error is. When ModuleID is blank (i.e. doesn't exist), Params["ModuleID"] returns null. — Stephen Chung
– Stephen Chung, Commented Apr 8, 2011 at 7:06

Jon Skeet · Accepted Answer · 2011-04-08 07:04:42Z

8

Just take out the call to ToString():

if (Request.Params["ModuleID"] == null)
{
    Response.Redirect("Content.aspx?ModuleID=1");
}

Currently you're trying to call ToString on a null reference.

This won't redirect if the ModuleID is present but empty though. You may want:

if (string.IsNullOrEmpty(Request.Params["ModuleID"]))
{
    Response.Redirect("Content.aspx?ModuleID=1");
}

answered Apr 8, 2011 at 7:04

Jon Skeet

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Comments

Wessel Kranenborg · Accepted Answer · 2011-04-08 07:07:32Z

2

You have to check the Request.Params["ModuleID"] on null. An null does not have a .ToString(), that is why you get this exception. If you use the following code you should not get an NullReferenceException.

if (Request.Url.ToString().ToLower().Contains("content.aspx")) 
{ 
    if (Request.Params["ModuleID"] == null) 
    { 
        Response.Redirect("Content.aspx?ModuleID=1"); 
    } 
}

answered Apr 8, 2011 at 7:07

Wessel Kranenborg

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