Hi. I Self Solved The Problem :
First I Add a GridView in My Form
Then I Changed Codes As Follow:
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
dbmanager dbm = new dbmanager();
dbm.loaddataingrid("select * from dieh", GridView1);
dbm.fillddl(DropDownList1, "my_tbl", "year", "id");
dbm.fillddl(DropDownList2, "my_tbl", "year", "id");
dbm.fillddl(DropDownList3, "my_tbl", "year", "id");
dbm.fillddl(DropDownList4, "my_tbl", "year", "id");
}
}
and :
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
string i = DropDownList1.SelectedIndex.ToString();
Label1.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text;
}
protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
{
string i = DropDownList2.SelectedIndex.ToString();
Label2.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text;
}
protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)
{
string i = DropDownList3.SelectedIndex.ToString();
Label3.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text;
}
protected void DropDownList4_SelectedIndexChanged(object sender, EventArgs e)
{
string i = DropDownList4.SelectedIndex.ToString();
Label4.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text;
}