exception handling

try
{
   // Problematic code goes here (i.e. opening a file, connecting to a database).
}
catch
{
   // An error has been detected. You can deal with it here.
}
finally
{
   // Clean up code here, regardless of whether or not there is an error
}

for example

if (IsPostBack == false)
        {
            try
            {
                SqlConnection con = new SqlConnection(Data.connect);
                SqlDataAdapter da = new SqlDataAdapter("select * from StudI", con);
                SqlCommandBuilder cm = new SqlCommandBuilder(da);
                DataSet ds = new DataSet();
                da.Fill(ds, "Stud_Info");
                if (ds.Tables["Stud_Info"].Rows.Count > 0)
                {
                    GridView1.DataSource = ds.Tables["Stud_Info"];
                    GridView1.DataBind();
                }
            }
            catch(Exception ex)
            {
                ClientScript.RegisterClientScriptBlock(GetType(), "Javascript", "<script>alert(' " + ex.Message.ToString() + "')</script>");
            }
        }