Question

I have a Form where I am inserting a record into the database. There are two tables, table_1 is called members, and table_2 is called Amount.

I am using two SQL INSERT statements to send records to database , because that’s the way I have figured out — there might be other ways, which I don’t know.

When I insert the record I get a message that it is inserted successfully, but when I check the database the inserted record replaces the one present , so I have last record in the DB repeated several times. Please assist.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace CemiyetAidatSistem
{
    public partial class AddMember : Form
    {
        public AddMember()
        {
            InitializeComponent();
        }
        SqlConnection con = new SqlConnection("Data Source=My-PC\\SQLSERVER;Initial Catalog=FredericiaDernek;Integrated Security=True");

        private void btnInsert_Click(object sender, EventArgs e)
        {
            SqlCommand cmd = new SqlCommand();
            string Sql = "INSERT INTO Uyeleri ( dID, FullName, Address, Mobile, Email, Comments ) VALUES ('" + txtdID.Text + "', '" + txtAdiSoyadi.Text + "','" + txtAddress.Text + "','" + txtMobile.Text + "','" + txtEmail.Text + "','" + txtComments.Text + "')";
            cmd.CommandText = Sql;
            cmd.Connection = con;
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();

            Sql = "INSERT INTO Aidat (dID Year, Amount ) VALUES ('"+ txtdID.Text +"','" + txtYear.Text + "','" + txtAmount.Text + "')";
            cmd.CommandText = Sql;
            cmd.Connection = con;
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();

            for (int i = 0; i < this.Controls.Count; i++)
            {
                if (this.Controls[i] is TextBox)
                {
                    this.Controls[i].Text = "";
                }
            }
            MessageBox.Show("Data Added Scuessfully");
        }

    }
}

Answer 1

I have rewritten your code to correct errors and bad practices

string connString = "Data Source=My-PC\\SQLSERVER;Initial Catalog=FredericiaDernek;Integrated Security=True";

private void btnInsert_Click(object sender, EventArgs e)
{
    using(SqlConnection con = new SqlConnection(connString))
    {
        con.Open();
        string Sql = "INSERT INTO Uyeleri (dID, FullName, Address, Mobile, Email, Comments ) " + 
                     "VALUES (@id, @name, @address, @mobile, @email, @comments");
        using(SqlCommand cmd = new SqlCommand(Sql, con))
        {
            cmd.Parameters.AddWithValue("@id", txtdID.Text);
            cmd.Parameters.AddWithValue("@name", txtAdiSoyadi.Text);
            cmd.Parameters.AddWithValue("@address", txtAddress.Text);
            cmd.Parameters.AddWithValue("@mobile", txtMobile.Text);
            cmd.Parameters.AddWithValue("@email", txtEmail.Text);
            cmd.Parameters.AddWithValue("@comments", txtComments.Text);
            cmd.ExecuteNonQuery();

            Sql = "INSERT INTO Aidat (dID, [Year], Amount ) VALUES " + 
                  "(@id, @year, @amount)";
            cmd.Parameters.Clear();
            cmd.CommandText = Sql;  // <- missing this in the previous version.....
            cmd.Parameters.AddWithValue("@id", txtdID.Text);
            cmd.Parameters.AddWithValue("@name", txtYear.Text);
            cmd.Parameters.AddWithValue("@amount", txtAmount.Text);
            cmd.ExecuteNonQuery();
        }
    }

What I have changed:

• The second insert statement is wrong. Missing a comma between first
  and second column
• Removed the creation of the SqlConnection at the global level
• Added appropriate using statement to dispose the SqlConnection and
  SqlCommand also in case of exceptions
• Used parameters for the two insert statements
• Added square brackets around Year field (Year is a reserved keyword
  in T-SQL)

Creating a SqlConnection at the global level is bad, because you grab system resources and you don’t dispose them for the lifetime of your application. And the situation could be out of control in case of exceptions not correctly handled.

Now I have some doubt about your tables. The fields dID (both tables) and Amount are of text type (varchar,nvarchar)?. If they are of numeric type it is necessary to add a conversion before adding the values to the Parameters collection