CODEWITHSUNDEEP
c#combobox
Gary
Gary

Reputation: 495

Setting ComboBox SelectedIndex to 0 after adding items throws exception

It's one of those days when even the simplest things don't work. TGIF. Consider the following code to populate a combobox which has been placed on a form using the designer:

   cboDisposition.Items.Add("Choose");  
   cboDisposition.Items.Add("Use as Is");  
   cboDisposition.Items.Add("Rework");  
   cboDisposition.Items.Add("Scrap");  
   cboDisposition.Items.Add("Return to Vendor");  
   cboDisposition.Items.Add("Void");  
   cboDisposition.DropDownStyle = ComboBoxStyle.DropDownList;

   cboDisposition.SelectedIndex = 0;

Setting the SelectedIndex causes an exception: ex = {"Object reference not set to an instance of an object."}

and the SelectedIndex is set to -1. Setting the value to any other integer between 1 and 5 works fine. Why is this happening?

Thanks for any advice.

Upvotes: 0

Views: 6624

Answers (2)

Joe
Joe

Reputation: 1

At the end, use the CreateControl method to refresh the list of options in the combo box.

cboDisposition.CreateControl();

cboDisposition.SelectedIndex = 0;

Then it won't throw an error.

Upvotes: 0

mcsilvio
mcsilvio

Reputation: 1098

This code looks OK. I suspect that you have an event handler for SelectedIndexChanged, and that something in there is throwing the exception. The Microsoft docs say that 0 is a valid index to specify. In the case that there aren't any elements in the combobox, you should have received a ArgumentOutOfRangeException instead.

Upvotes: 5

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