selecting one dropdown then fired second dropdown in gridview

1st u should write the code for ddldept by using<asp:listitem>---</asp:listitem> or Byusing Dataset then ddldept events will be displayed

I will give one example this is same as ajax cascading bt directly come
1 is Countryddl & 2nd Stateddl If we select country then related states only displayed.
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
GetData();
}
}

void GetData()
{
try
{

string command = "select CountryId,CountryName From Country Order by CountryName";
da = new SqlDataAdapter(command, con);
ds = new DataSet();
da.Fill(ds, "Country");
CountryDropDownList.DataSource = ds;
CountryDropDownList.DataValueField = ds.Tables[0].Columns[0].ToString();
CountryDropDownList.DataTextField = ds.Tables[0].Columns[1].ToString();
CountryDropDownList.DataBind();
CountryDropDownList.Items.Insert(0, new ListItem("-- Select Category --", "0"));


}
catch (Exception ce)
{
MsgLabel.Text = ce.Message;
}
}

protected void CountryDropDownList_SelectedIndexChanged(object sender, EventArgs e)
{
StateDropDownList.Enabled = true;
{
try
{
string command = "select StateId,StateName From State where Countryid="+CountryDropDownList.SelectedValue+ "Order by StateName";
da = new SqlDataAdapter(command, con);
ds = new DataSet();
da.Fill(ds, "State");
StateDropDownList.DataSource = ds;
StateDropDownList.DataValueField = ds.Tables[0].Columns[0].ToString();
StateDropDownList.DataTextField = ds.Tables[0].Columns[1].ToString();
StateDropDownList.DataBind();
StateDropDownList.Items.Insert(0, new ListItem("-- Select Category --", "0"));

}
catch (Exception ce)
{
MsgLabel.Text = ce.Message;
}
}

}