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]]

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?

 

[AvdP]

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 !

 

[=?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";

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

 

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

Hi,

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]

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]]

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

 

[Quoc Linh]

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

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

 

[Quoc Linh]

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.

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 !

 

[Zeba]

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

Thanks all of ya!

 

[Zeba]

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

Thanks all of ya!