how to print sum(amount) in label

Question

i want to print a sum (amount) in label windows form --- from sql 

 

my code is ... it is not working 

 

 i

SqlCommand com = new SqlCommand("SELECT sum(amount) from custpurches where name='" + comboBox1.Text + "'", con);

try

{

con.Open();

SqlDataReader dr = com.ExecuteReader();

con.Close();

if (dr.Read())

{

label1.Text = dr["amount"].ToString();

dr.Close();

con.Close();

}

else

{

MessageBox.Show("error");

dr.Close();

con.Close();

}

}

catch (Exception ex)

{

MessageBox.Show("Try again or Refresh", "message");

}