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General .NET For general discussion of MICROSOFT .NET topics that don't fall within any of the other .NET forum subcategories or .NET language forums.  If your question is specific to a language (C# or Visual Basic) or type of application (Windows Forms or ASP.Net) try an applicable forum category. ** PLEASE BE SPECIFIC WITH YOUR QUESTION ** When posting here, provide details regarding the Microsoft .NET language you are using and/or what type of application (Windows/Web Forms, etc) you are working in, if applicable to the question. This will help others answer the question without having to ask.
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Old June 5th, 2005, 11:41 AM
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Default <undefined value>

How do I test for <undefined value> in an if statement?

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Old June 6th, 2005, 07:23 AM
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hi

Check if (x == null) -> C#

Prashant

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Old June 6th, 2005, 07:27 AM
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No, already tried that.

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Old June 6th, 2005, 11:32 PM
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hi,

What Error you are getting,also which is the language?
Just post a few lines of code of the function to use this.

Prashant
Prashant

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Old June 7th, 2005, 07:19 AM
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C#

private void listBox1_SelectedIndexChanged(object sender, System.EventArgs e){
collectLink(listBox1.SelectedItem.ToString());
listBox1.Items.Remove(listBox1.SelectedItem);
}

collectLink(listBox1.SelectedItem.ToString()); throws a

An unhandled exception of type 'System.NullReferenceException' occurred in WindowsApplication2.exe Additional information: Object reference not set to an instance of an object.

if(listBox1.SelectedItem.ToString()!=null){
collectLink(listBox1.SelectedItem.ToString());
listBox1.Items.Remove(listBox1.SelectedItem);
}
also throws the same exception.

After stepping through it, I found that it accesses the selectedIndexChange twice. On the second time, it throws the exception at listBox1.SelectedItem.ToString()!=null.
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Old June 7th, 2005, 01:02 PM
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Default

Often on listboxes, you need to check for SelectedItem being null becauase you can have no selected item in a listbox.

if(listBox1.SelectedItem!=null){
  collectLink(listBox1.SelectedItem.ToString());
  listBox1.Items.Remove(listBox1.SelectedItem);
}

-Peter
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