c# How to show name and insert values (name's ID ) from combobox in c#

Question

Thank you guys in advance. I'am new user in c# Windows Forms.

I have a table with id's and name

ID  | Name
---------------
1   | Lion
2   | Tiger
3   | Crocodile

If I want to display from a table to combobox I did like this.

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

namespace Insert_update_delete_nr2
{
    public partial class Form1 : Form
    {
        SqlConnection con = new SqlConnection(@"CONNECTION_STRING");

        SqlCommand cmd = new SqlCommand();
        SqlDataReader dr;
        public Form1()
        {
            InitializeComponent();
        }


        private void button1_Click_1(object sender, EventArgs e)
        {

                con.Open();

                string query = "select * from info";
                SqlCommand cmd = new SqlCommand(query, con);
                cmd.CommandType = CommandType.Text;
                dr = cmd.ExecuteReader();


                while (dr.Read())//while true
                {

                    comboBox1.Items.Add(dr[0].ToString());//loading values into combo
                }

                cmd.CommandText = "insert into info3 (name, name_id) values ('"+textBox1.Text+"', '" + comboBox1.Items.Add(dr[0].ToString()) + "')";
                cmd.ExecuteNonQuery();

                cmd.Clone();
                con.Close();

        }

        private void loadlist()
        {
            listBox1.Items.Clear();
            listBox2.Items.Clear();
            listBox3.Items.Clear();
            con.Open();

            cmd.CommandText = "select * from info3";
             dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    listBox1.Items.Add(dr[0].ToString());
                    listBox2.Items.Add(dr[1]).ToString();
                    listBox3.Items.Add(dr[3].ToString());


                }
            }
            con.Close();


        }

        private void Form1_Load(object sender, EventArgs e)
    {

       // con.Open();
        FillDropDownList(string SQL, ComboBox comboBox1);// This giving me error.
        // How should I call this FillDropDownlist function? The parameters which are they?
        cmd.Connection = con;
        listBox3.Visible = false;

        loadlist();

    }



    }
}

And it's trying inserting what is showing in combobox which it's name, not id's.

in PHP it would be like the following:

$sql =  " SELECT * FROM info ";
$res = mysql_query($sql);
while ($row = mysql_fetch_array($res)) {
    print '<option value="'.$row['id'].'">'.$row['name'].'</option>';
}

That would insert id's and showing names. But How should I do in c#? Thank you again for your time!

Answer 1

Instead of adding the name string to the combobox, you could add a custom type, instead:

class Animal
{
    public int ID { get; set; }
    public string Name { get; set; }

    public override string ToString()
    {
        return Name;
    }
}

Create an object of that type for each entry (var animal = new Animal { ID = (int)dr[0], Name = (string)dr[1] };), add the object to the combobox. Then when you go to retrieve it, simply cast the item to an Animal type and grab the ID.

var animal = (Animal)comboBox1.SelectedItem;

Answer 2

If I understand your question correctly, this should do what you are seeking:

Load your combo box with something like THIS (I can't test this right now, so I may have made some typo's or minor syntax errors):

**UPDATED: Ok. That is the LAST time I try to answer a question "on the go" when I'm in a rush. My original code was rife with issues and stupid typos. My sincere apologies! The following code includes a very basic version of everything you are trying to do. You may need to adapt it to suit your needs.

Some suggestions:

A. Place your connection and command in the using blocks, as shown.

B. Instead of hard-coding your connection string in your code, use the Properties.Settings designer in the Solutions Explorer (off to the left) and create a central reference for your connection string. Then reference it in code like shown.

The following performs the basic functionality you are trying to achieve, and runs on my machine:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }


    private void Form1_Load(object sender, EventArgs e)
    {
        button1.Click += new EventHandler(button1_Click);
        this.FillDropDownList();
    }


    void button1_Click(object sender, EventArgs e)
    {
        this.SaveComboBoxContent();
    }


    public void FillDropDownList()
    {
        string SQL = "SELECT id, name FROM info ORDER BY name";

        DataTable dt = new DataTable();

        // Set the connection string in the Solutions Explorer/Properties/Settings object (double-click)
        using (var cn = new SqlConnection(Properties.Settings.Default.MyConnectionString))
        {
            using(var cmd = new SqlCommand(SQL, cn))
            {
                cn.Open();

                try
                {
                    dt.Load(cmd.ExecuteReader());
                }
                catch (SqlException e)
                {
                    // Do some logging or something. 
                    MessageBox.Show("There was an error accessing your data. DETAIL: " + e.ToString());
                }
            }
        }

        // UPDATED - The .ValueMember and .DisplayMember properties 
        // refer to the string name of the field (oops!):
        comboBox1.DataSource = dt;
        comboBox1.ValueMember = "id";
        comboBox1.DisplayMember = "name";
    }


    public void SaveComboBoxContent()
    {
        string SQL = "INSERT INTO info2 (name_id) VALUES (@name_id)";

        using (var cn = new SqlConnection(Properties.Settings.Default.MyConnectionString))
        {
            using(var cmd = new SqlCommand(SQL, cn))
            {
                cmd.Parameters.AddWithValue("@name_id", comboBox1.SelectedValue);
                cn.Open();

                try
                {
                    cmd.ExecuteNonQuery();
                }
                catch (SqlException e)
                {
                    // Do some logging or something. 
                    MessageBox.Show("There was an error accessing your data. DETAIL: " + e.ToString());
                }
            }
        }
    }

}

Hope that helps.