Question

I’ve comboBox in windows forms which I’ve bound to datasource, which is correctly returning Id associated with particular name in combobox whenever form loads.

private void PurchaseMaster_Load(object sender, EventArgs e)
{
    DataTable dt = productMasterBAL.GetTable("Select * from productMaster");
    comboBox1.DataSource = dt;
    comboBox1.DisplayMember = "ProductName";
    combBox1.ValueMember = "ProductId";
}

But whenever I select any value in Combobox I get:

NullReferenceException was unhandled. Object reference not set to an
instance of an object

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{

           DataRowView row = comboBox1.SelectedValue as DataRowView;
           MessageBox.Show(String.Format("{0}", row["ProductId"])); //This line is causing exception
}

Could anyone please tell how can I solve this problem?

Answer 1

You should be checking for the values like this

private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
{
   ComboBox cmb = (ComboBox)sender;
   MessageBox.Show(cmb.SelectedValue.ToString());// cmb.SelectedText
}

This should give you the selected Product Id in the combobox

The items in Combobox are stored as ObjectCollection and not exactly a DataRow or DataRowView as you seem to be expecting.