Why ComboBox items need to be reselected to obtain Value? - asp.net

Question

I am using ext.net 1.3 controls in my ASP.NET 4.0 application. I have several ComboBox controls on my Web Form. The page is supposed to perform two tasks, Insert and Update. There are no issues when a new record is saved, but when I try to fill the ComboBox controls with an existing database values, various issues pop up. The most troubling is this one:
The ComboBox displays the Text from the database, but it neither gets populated nor I am able to pick the ComboBox Value Member. This is because it is not populated. I have written code to populate ComboBox in the Page Load event.
I am using this code to pick a value from the database and show it on the ComboBox:
string Query = "SELECT CustName FROM CustomerMaster WHERE CustID = " + Session["CustomerID"];
var result = DB.Single<Customer>(Query);
CustomerComboBox.setValue = result.CustName;
This code successfully retrieves the Customer Name and displays in the ComboBox. What it is not doing is that it is not selecting from the ComboBox Item List and neither populating the ComboBox.
If I try to retrieve the Value Member of the Text using:
CustomerComboBox.SelectedItem.Value;
it gives error.
To make it work, I need to click on the ComboBox again to make it populate and than I manually select the same customer name from the list to pick the value.
How to get rid of this issue?
-- Edited --
The code to fill ext.net ComboBox is this:
public void FillExtComboList(string ParameterFlag, ComboBox DropDownName)
{
string Query = "";
using (TransactionScope transactionScope = new TransactionScope())
{
using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["cncustomer"].ConnectionString.ToString()))
{
con.Open();
SqlDataReader dr;
try
{
if (ParameterFlag == "Customer")
{
Query = "SELECT CustName FROM CustomerMaster";
}
//Check whether the Drop Down has existing items. If YES, empty it.
if (DropDownName.Items.Count > 0)
DropDownName.Items.Clear();
SqlCommand cmd = new SqlCommand(Query, con);
dr = cmd.ExecuteReader();
while (dr.Read())
{
Ext.Net.ListItem extLI = new Ext.Net.ListItem();
extLI.Text = dr[0].ToString();
DropDownName.Items.Add(extLI);
}
dr.Close();
con.Close();
}
catch (Exception ex)
{
con.Close();
// RunCustomScript("alert('" + ex.Message.ToString() + "')", callingPageObjectName);
}
} /* End of SQL Connection */
transactionScope.Complete();
} /* End of Transaction Scope */
}
On Page Load event, the ComboBox control is filled with above method.

Answer 1

I don't see an instruction to fill the combo box, only to set its selected value. Arent you missing a CustomerComboBox.DataSource = someList or something like that?
<-- EDIT -->
Sorry, I thought the setValue was the code on your page load...
OK, this is not be the answer to your problem, but an important performance fix.
you should do this when loading the combo:
when executing the SQL Query:
Query = "SELECT CustID, CustName FROM CustomerMaster"
when filling the combo:
Ext.Net.ListItem extLI = new Ext.Net.ListItem();
extLI.Value = dr["CustId"].ToString();
extLI.Text = dr["CustName"].ToString();
DropDownName.Items.Add(extLI);
so when you want to select an item, you just do this:
CustomerComboBox.setValue = Session["CustomerID"];
and avoid going back to the database to get the customer name.
Now, could you share the code you have to handle the combobox click? Since it does fill the combo, it may throw some ligth to us. Also, try adding
CustomerComboBox.DataBind()
And, come to think of it, I see on Page_Load you use "DropDownName" and later on you use "CustomerComboBox". Could that be the problem?

Answer 2

If I understand you correctly try this code:
protected void Page_Load(object sender, EventArgs e) {
FillExtComboList(DropDownName);
// Set value that you want
DropDownName.SetValueAndFireSelect("Test 3");
}
public void FillExtComboList(ComboBox DropDownName) {
try {
//Check whether the Drop Down has existing items. If YES, empty it.
if (DropDownName.Items.Count > 0)
DropDownName.Items.Clear();
for (int i = 0; i < 10; i++) {
Ext.Net.ListItem extLI = new Ext.Net.ListItem();
extLI.Text = "Test " + i;
DropDownName.Items.Add(extLI);
}
} catch (Exception ex) {
// RunCustomScript("alert('" + ex.Message.ToString() + "')", callingPageObjectName);
} /* End of Transaction Scope */
}