I'm not really a fan of SqlDataSource, but if you are trying to extract the value from your SqlDataSource so you can use it to populate your DropDown then you could try something like this:
protected void Page_Load(object sender, EventArgs e)
{
DataView dvSql = (DataView)SqlDataSource8.Select(DataSourceSelectArguments.Empty);
foreach (DataRowView drvSql in dvSql)
{
string moduleName = drvSql["MName"].ToString();
DropDownList1.Items.Clear();
DropDownList1.Items.Add(moduleName);
}
}