Click the option in the listbox to display it directly in the textbox

When an option in the listbox is clicked, it is displayed in the textbox. This needs to change the property AutoPostBack of the listbox to true

Add code to the Selectedindexchanged event of the listbox

if(this.ListBox1 .SelectedItem !=null )
{

this.textbox.text=this.listbox1.selecteditem.text;

}

When there are two listboxes, the first is the type of the second, and the content of the second is displayed in the textbox

if (this.ListBox1.SelectedValue == "TeacherId")//teacherid is the value of the option in listbox1
{
ListBox2.Items.Clear(); //First clear listbox2 to remove redundant content

string strSQL = "SELECT TeacherId,TeacherName FROM teacher_infotable;";

DataSet ds = db.GetDataSet(strSQL);
DataTable dt = ds.Tables[0];
if (dt.Rows.Count > 0)
{
for (int i = 0; i < dt.Rows.Count; i++)
{
ListItem lt = new ListItem();
lt.Value = dt.Rows[i].ItemArray[0].ToString();
lt.Text = dt.Rows[i].ItemArray[1].ToString();

this.ListBox2.Items.Add(lt);
}
}
}

 

Event code for listbox2

foreach (ListItem li in ListBox2.Items)
{
if (li.Selected)
{
this.txt_MessageClassIdentifier.Text += li.Value +",";
}
}

The effect is as follows; here is the ID, not the text, adjust it according to your needs