NullRefrenceException was unhandled by user code

Question

Code below is placed in page_Load. How I should handle this to bypass UrlReferrer when you enter page directly first time and there is no referrer? What I am missing here?

    if (HttpContext.Current.Request.UrlReferrer.AbsoluteUri != null)
    {
        urlReferer = HttpContext.Current.Request.UrlReferrer.AbsoluteUri.ToString();
    }
    else
    {
        urlReferer = "";
    }

sll · Accepted Answer · 2012-07-11 14:19:59Z

5

Just check UrlReferrerfor null:

if (HttpContext.Current.Request.UrlReferrer != null 
    && HttpContext.Current.Request.UrlReferrer.AbsoluteUri != null)
{
     urlReferer = HttpContext.Current.Request.UrlReferrer.AbsoluteUri.ToString();
}     
else     
{         
    urlReferer = "";     
}

answered Jul 11, 2012 at 14:19

sll

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1 Comment

laspalmos Over a year ago

When try to check for if(HttpContext.Current.Request.UrlReferrer.AbsoluteUri != Null) then throws the NullReferenceException - Object reference not set to an instance of an object so I can't use this syntax but checking for if (HttpContext.Current.Request.UrlReferrer != null ) is working in my code also placing it in (!IsPostBack) makes it even better.

Shai · Accepted Answer · 2012-07-11 14:19:40Z

3

Who says the client passed by the referrer in the HTTP request?

Check if UrlReferrer is null first

if (HttpContext.Current.Request.UrlReferrer != null)
    {
        urlReferer = HttpContext.Current.Request.UrlReferrer.AbsoluteUri.ToString();
    }
    else
    {
        urlReferer = "";
    }

answered Jul 11, 2012 at 14:19

Shai

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1 Comment

sll Over a year ago

This will throw NullReferenceException if HttpContext.Current.Request.UrlReferrer.AbsoluteUri == null

David Yaw · Accepted Answer · 2012-07-11 15:22:15Z

2

Why not this way much cleaner than checking nulls

private void Page_Load()
{
    if (!IsPostBack)
    {
        if (HttpContext.Current.Request.UrlReferrer != null)
        {
            urlReferer = HttpContext.Current.Request.UrlReferrer.AbsoluteUri.ToString();
        }
        else
        {
            urlReferer = "";
        }
    }
}

edited Jul 11, 2012 at 15:22

David Yaw

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answered Jul 11, 2012 at 14:25

HatSoft

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Comments

David Yaw · Accepted Answer · 2012-07-11 14:19:48Z

2

I believe you need to check if HttpContext.Current.Request.UrlReferrer != null.

answered Jul 11, 2012 at 14:19

David Yaw

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Comments

James Osborn · Accepted Answer · 2012-07-11 14:20:23Z

0

If UrlReferrer is null, then the test to AbsolutUri will fail.

Try initially testing UrlReferrer for null, this will probably correct the issue.

answered Jul 11, 2012 at 14:20

James Osborn

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Comments

Sam I am says Reinstate Monica · Accepted Answer · 2012-07-11 14:22:09Z

0

Use your debugger. If you're running this out of visual studio, than you might be brought to a debugger window when the exception is thrown. There are multiple tabs at the bottom of the debugger including "Locals" and "Watch" you can use those to see what variables are being stored.

If the above code is indeed what's causing the problem than

HttpContext.Current.Request.UrlReferrer.AbsoluteUri
or
HttpContext.Current.Request.UrlReferrer
or
HttpContext.Current.Request
or
HttpContext.Current
or
HttpContext

is set to null

answered Jul 11, 2012 at 14:22

Sam I am says Reinstate Monica

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