Null reference exception - Query string

[Zeba]

Hi ....

I'm always getting stuck with null reference exceptions !

Can you tell me what's wrong with my code given below ? I'm getting
the error that reference is not set to an instance of an object.
protected void Page_Load(object sender, EventArgs e)
{
String myItem;
if (Request.QueryString["Item"].ToString() != null)
{
myItem = Request.QueryString["Item"].ToString();
Label1.Text = myItem;
}
else
{
Label1.Text = "none";
}
}

Thanks !

[Jon Skeet [C# MVP]]

Zeba <co******@gmail.comwrote:

I'm always getting stuck with null reference exceptions !

Can you tell me what's wrong with my code given below ? I'm getting
the error that reference is not set to an instance of an object.

On which line? If it's a line with multiple expressions on, have you
tried breaking it down into multiple lines so you can find out exactly
which expression is null?

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[AvdP]

"Zeba" <co******@gmail.comschreef in bericht
news:11**********************@q2g2000cwa.googlegro ups.com...

Hi ....

I'm always getting stuck with null reference exceptions !

Can you tell me what's wrong with my code given below ? I'm getting
the error that reference is not set to an instance of an object.
protected void Page_Load(object sender, EventArgs e)
{
String myItem;
if (Request.QueryString["Item"].ToString() != null)
{
myItem = Request.QueryString["Item"].ToString();
Label1.Text = myItem;
}
else
{
Label1.Text = "none";
}
}

Thanks !

Hi,

Probably Request.QueryString["Item"] evaluates to null.
You better change your code in something like:

protected void Page_Load(object sender, EventArgs e)
{
String myItem;
if(Request.QueryString["Item"] != null)
{
myItem = Request.QueryString["Item"].ToString() ;
Label1.Text = myItem ;
}
else
{
Label1.Text = "none";
}
}

or save some bytes this way:

protected void Page_Load(object sender, EventArgs e)
{
Label1.Text = Request.QueryString["Item"] != null ?
Request.QueryString["Item"].ToString() : "none";
}
Regards,
Anne

[Zeba]

Okayy..! That has solved the problem...So it was ToString() which was
complaining of null reference object, wasn't it..
Thanks !

Hi,

Probably Request.QueryString["Item"] evaluates to null.
You better change your code in something like:

protected void Page_Load(object sender, EventArgs e)
{
String myItem;
if(Request.QueryString["Item"] != null)
{
myItem = Request.QueryString["Item"].ToString() ;
Label1.Text = myItem ;
}
else
{
Label1.Text = "none";
}

}

or save some bytes this way:

protected void Page_Load(object sender, EventArgs e)
{
Label1.Text = Request.QueryString["Item"] != null ?
Request.QueryString["Item"].ToString() : "none";

}

Regards,
Anne

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Yes, it was.

Here's an even shorter way of writing the code:

Label1.Text = Request.QueryString["Item"] ?? "none";

:)

Zeba wrote:

Okayy..! That has solved the problem...So it was ToString() which was
complaining of null reference object, wasn't it..
Thanks !

>Hi,

Probably Request.QueryString["Item"] evaluates to null.
You better change your code in something like:

protected void Page_Load(object sender, EventArgs e)
{
String myItem;
if(Request.QueryString["Item"] != null)
{
myItem = Request.QueryString["Item"].ToString() ;
Label1.Text = myItem ;
}
else
{
Label1.Text = "none";
}

}

or save some bytes this way:

protected void Page_Load(object sender, EventArgs e)
{
Label1.Text = Request.QueryString["Item"] != null ?
Request.QueryString["Item"].ToString() : "none";

}

Regards,
Anne

--
Göran Andersson
_____
http://www.guffa.com

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

"Zeba" <co******@gmail.comwrote in message
news:11**********************@q2g2000cwa.googlegro ups.com...

Hi ....

I'm always getting stuck with null reference exceptions !

Can you tell me what's wrong with my code given below ? I'm getting
the error that reference is not set to an instance of an object.
protected void Page_Load(object sender, EventArgs e)
{
String myItem;
if (Request.QueryString["Item"].ToString() != null)

This may be the line, look into the docs what happens if "Item" does not
exist in the collection

[Quoc Linh]

On Feb 23, 4:50 am, Göran Andersson <[e-mail]:

Yes, it was.

Here's an even shorter way of writing the code:

Label1.Text = Request.QueryString["Item"] ?? "none";

:)

What, this works? Would be nice... :) I thought in C#, we have to
explicit compares to null?

Quoc Linh

[Jon Skeet [C# MVP]]

Quoc Linh <le********@yahoo.comwrote:

On Feb 23, 4:50 am, Göran Andersson <[e-mail]:

Yes, it was.

Here's an even shorter way of writing the code:

Label1.Text = Request.QueryString["Item"] ?? "none";

:)

What, this works? Would be nice... :) I thought in C#, we have to
explicit compares to null?

?? is the null coalescing operator.

See http://pobox.com/~skeet/csharp/csharp2/nullable.html

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Quoc Linh]

On Mar 1, 12:22 pm, Jon Skeet [C# MVP] <[e-mail]:

Quoc Linh <[e-mail]:

On Feb 23, 4:50 am, Göran Andersson <[e-mail]:

Yes, it was.

Here's an even shorter way of writing the code:

Label1.Text = Request.QueryString["Item"] ?? "none";

:)

What, this works? Would be nice... :) I thought in C#, we have to
explicit compares to null?

?? is the null coalescing operator.

Seehttp://pobox.com/~skeet/csharp/csharp2/nullable.html

--
Jon Skeet - <[e-mail]>http://www.pobox.com/~skeet Blog:http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

I did not know that. Very useful tip. Thanks Jon!

[Quoc Linh]

On Mar 1, 1:52 pm, "Quoc Linh" <[e-mail]:

On Mar 1, 12:22 pm, Jon Skeet [C# MVP] <[e-mail]:

Quoc Linh <[e-mail]:

On Feb 23, 4:50 am, Göran Andersson <[e-mail]:
Yes, it was.

Here's an even shorter way of writing the code:

Label1.Text = Request.QueryString["Item"] ?? "none";

:)

What, this works? Would be nice... :) I thought in C#, we have to
explicit compares to null?

?? is the null coalescing operator.

Seehttp://pobox.com/~skeet/csharp/csharp2/nullable.html

--
Jon Skeet - <[e-mail]>http://www.pobox.com/~skeet Blog:http://www..msmvps.com/jon.skeet
If replying to the group, please do not mail me too

I did not know that. Very useful tip. Thanks Jon!

Oh, and thanks Goran for bringing up the original code ! :)

Quoc Linh

[Zeba]

Hey that article was really interesting. Earlier I hadn't understood
how Goran's code did its work.

Thanks !

?? is the null coalescing operator.

Seehttp://pobox.com/~skeet/csharp/csharp2/nullable.html

[Zeba]

Hey that article was really interesting. Earlier I hadn't understood
how Goran's code did its work.

Thanks all of ya!

?? is the null coalescing operator.

Seehttp://pobox.com/~skeet/csharp/csharp2/nullable.html

[Zeba]

Hey that article was really interesting. Earlier I hadn't understood
how Goran's code did its work.

Thanks all of ya!

?? is the null coalescing operator.

Seehttp://pobox.com/~skeet/csharp/csharp2/nullable.html