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string.isNullOrEmpty(SelectedItem.Value) not work

Posted on 2009-05-20
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Last Modified: 2013-12-17
Hi

I have a drop down list in a aspx form which uses C#.

If I do not choose anything and pressed submit button, it throws nullreference exception.

But, I use the following code to check it in if condition and still not work.

How can I fix it?
string a = this.location.SelectedItem.Value;
if (string.IsNullOrEmpty(this.location.SelectedItem.Value) || this.location.SelectedItem.Value == null || this.location.SelectedItem.Value =="")

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Question by:techques
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4 Comments
 
LVL 29

Accepted Solution

by:
David H.H.Lee earned 25 total points
ID: 24429157
Hi techques,
Try this easier way:

string a = this.location.SelectedItem.Value.toString();
if(a=="")

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Assisted Solution

by:tetorvik
tetorvik earned 25 total points
ID: 24429254
i believe your dropdownlist SelectedItem is null, therefore you'll get the exception. You'll need to check that prior to access it's Value property

if(this.location.SelectedItem != null)
{

}
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Author Closing Comment

by:techques
ID: 31583380
both work, thanks for help
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LVL 8

Expert Comment

by:ppittle
ID: 24431941
Or try this.location.SelectedValue, which returns a string, so you don't need to check for a null reference, as long as you have a valid pointer to your drop down list
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