How do I get the selected values in a listbox?

Question

I have a Winforms applicaiton that has a listbox of values that can be selected. I want the selected values to show up on the editing form as selected. Here's the loading code:

ListBox Loading Code

private void LoadListBox()
{
    DataTable dt = new DataTable();
    string[] names = new string[] { "UID1", "UID2", "UID3","UID4" };
    dt.Columns.Add("Units", typeof(string));
    dt.Columns.Add("Value", typeof(int));
    int count = 1;
    foreach (string value in names)
    {
        DataRow drRow = dt.NewRow();
        drRow["Units"] = value;
        drRow["Value"] = count;
        count++;
        dt.Rows.Add(drRow);
    }
    listBox1.DisplayMember = "Units";
    listBox1.ValueMember = "Value";
    listBox1.DataSource = dt;
}

If they select UID1 and UID2 it is stored as 1 , 2 in the database.

If the user clicks on the edit button, then UID1 , UID2 should be the selected values, but all values should be loaded.

How do I make sure that whatever they've selected shows as selected when the edit button is clicked?

Answer 1

Enumerate each listbox item and set it as selected or not based on your rules:

for (int index = 0; index < listBox1.Items.Count; index++ )
{
   Object o = (int)listBox1.Items[index];
   if ( /* criteria you want here */ )
   {
       listBox1.SetSelected(index, true);

}

}

Answer 2

The selected values are preserved during Postback unless you're setting the data source in Postback event as well, thus "overwriting" it.

So just have such if statement in your code:

 
 
 
 
  
  
  if (!Page.IsPostBack) LoadListBox();
 
 
  

Sorry, thought it was ASP.NET - not relevant in WinForms environment. Other answers already give what you need. :)

Answer 3

Try the SelectedItems.Add funcion. You can add to the current selection every item you want.