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Not successful with SelectedIndex = -1 for Combobox

Posted By:      Posted Date: September 16, 2010    Points: 0   Category :Windows Application
My Windows form has three comboboxes. Combobox2 references a child table of combobox1, and Combobox3 references a child table of combobox2. I want the three comboboxes not to show a selectedItem until the user selects a value.  I have this set when the Form is first shown:         private void Form1_Shown(Object sender, EventArgs e)         {             this.comboBox1.SelectedIndex = -1;             MessageBox.Show("You are in the Form.Shown event.");         }          private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)         {             if (isClosing == false)             {                 try                 {                     String cb1Value = comboBox1.SelectedValue.ToString();     

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