1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:

   private void button1_Click(object sender, EventArgs e)
        {
            SqlConnection cs = new SqlConnection("Data Source=HELGA-PC; Initial Catalog = Dimi; Integrated Security = TRUE");
            SqlDataAdapter da = new SqlDataAdapter();
            da.InsertCommand = new SqlCommand("INSERT INTO tblcontacts  VALUES(@FIRSTNAME, @LASTNAME)", cs);
            da.InsertCommand.Parameters.Add("@FIRSTNAME", SqlDbType.VarChar).Value = txtFirstname.Text;
            da.InsertCommand.Parameters.Add("@LASTNAME", SqlDbType.VarChar).Value = txtLastname.Text;

            cs.Open();
            da.InsertCommand.ExecuteNonQuery();
            cs.Close();

        }
    }
}                    

1:

INSERT INTO tblcontacts (FIRSTNAME, LASTNAME) VALUES (@FIRSTNAME, @LASTNAME)