从GridView列中选择多个ListBox项

Question

I have a databound Listbox with Multiselect enabled. On page load, I feed the information from a GridView column and select all the options that match, using this code:

string[] separators = { "<br />" };

String Departments = Session["ProjDept"].ToString();
string[] splitDepartments = Departments.Split(separators, StringSplitOptions.RemoveEmptyEntries);
foreach (var dept in splitDepartments)
        {
            listDepartment.SelectedIndex = listDepartment.Items.IndexOf(listDepartment.Items.FindByText(dept));
        }

However, I am running into a strange issue: when there is only one department in the GridView column, the option in the listbox gets properly selected, but when there's multiple departments only the LAST department gets selected.

I've ran System.Diagnostics.Debug.Print(dept) within my foreach to ensure that all the values are getting passed and they all appear in the STDOUT, but the listbox still won't cooperate.

Any ideas as to how I can fix this -- or alternatively, what other code could I use to achieve the same results?

Thank you!

Answer 1

The SelectedIndex property only allows one value at a time, so you're resetting it with each iteration. That's why only the last one is being selected. You need to access the "Selected" property from the ListItem itself.

Without trying it myself, it should look something like:

foreach (var dept in splitDepartments)
{
     int index = listDepartment.Items.IndexOf(listDepartment.Items.FindByText(dept));        
     listDepartment.Items[index].Selected = true;
}

As long as you do have SelectionMode="Multiple" - that code should work.