how to create relationship between two combo box in c# winform application

Question

I need to create two combo box and when i select a value in combo box 1, a related value should display in combo box 2. the Values are taken from two different database table (deviceCat and Device). Please i need help on this for my C# winform application. I am a newbie to c# Programming. thanks.

score 1 · Answer 1 · answered Mar 06 '15 at 11:44

using System;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            comboBox1.Items.Add("weekdays");
            comboBox1.Items.Add("year");
        }
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            comboBox2.Items.Clear();
            if (comboBox1.SelectedItem == "weekdays")
            {
                comboBox2.Items.Add("Sunday");
                comboBox2.Items.Add("Monday");
                comboBox2.Items.Add("Tuesday");
            }
            else if (comboBox1.SelectedItem == "year")
            {
                comboBox2.Items.Add("2012");
                comboBox2.Items.Add("2013");
                comboBox2.Items.Add("2014");
            }
        }
    }
}

You can use this link [link](http://stackoverflow.com/questions/25216492/how-to-retrieve-tables-of-a-database-in-a-combobox-using-an-windows-form-applica) and this [link](http://stackoverflow.com/questions/27597250/how-bind-database-values-to-combo-box-in-windows-appliation) and this [link](http://stackoverflow.com/questions/7423911/how-to-populate-c-sharp-windows-forms-combobox) — Alireza Hosseinitabar, Mar 06 '15 at 12:00

score 0 · Answer 2 · edited Sep 02 '19 at 08:15

0

you can use the OnSelectedValueChanged event handler to trigger the code to clear and re populate the data in the second combobox

edited Sep 02 '19 at 08:15

Hasta Dhana

4,699
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answered Mar 06 '15 at 11:20

Ewan

1,261
1
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25

Can you help with a sample code?. thanks – Umar E. Shaibu Mar 06 '15 at 11:22

score 0 · Answer 3 · answered Mar 06 '15 at 11:33

    private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        switch (comboBox1.Text)
        {
            case "Something":
                comboBox2.Items.Clear();
                comboBox2.Items.Add("Option1");
                comboBox2.Items.Add("Option2");
                comboBox2.Items.Add("Option3");
                break;
            case "Something else":
                comboBox2.Items.Clear();
                comboBox2.Items.Add("Option4");
                comboBox2.Items.Add("Option5");
                comboBox2.Items.Add("Option6");
                break;
            default:
                break;
        }

    }

If you do something like this it should work. What this does is it checks the text in the combobox1 and then modifies the text of the second one accordingly

score 0 · Answer 4 · answered Mar 06 '15 at 11:34

Just a quick mockup:

var cb1 = new ComboBox();
var cb2 = new ComboBox();

cb1.Items.AddRange(firstItems); // whatever you want to put into the first ComboBox
cb2.Items.AddRange(secondItems); // whatever you want to put into the second ComboBox

public void ChangeSelectionInSecondComboBox(object sender, EventArgs e)
{
    var selectedItem = cb1.SelectedItem;
    if(selectedItem == [...]) // depends on how you want to decide which item 
                                 to display in ComboBox2
    {
        cb2.SelectedIndex = [...] // you need to decide which Index to set
    }
}

cb1.SelectedIndexChanged += ChangeSelectionInSecondComboBox;

Essentially, what you want is to listen to the SelectionChanged event of your first ComboBox and then select the relevant item in the second ComboBox.

score 0 · Answer 5 · answered Mar 06 '15 at 12:21

You simply need to take advantage of the selectIndexChanged event of your master combobox to update the selectedItem from your dependant combobox.

Here is an illustration. I have two classes. A client class and a Contract class. Every client has a contract

Here is the Contract class:

 public class Contract
 {

     public String ContractNumber { get; set; }
     public Contract(String contractNumber)
     {
         ContractNumber = contractNumber;
     }

     public override string ToString()
     {

         return "Contract Number :" + ContractNumber;
     }
 }

And here is the Client class:

 public class Client
 {
     public String Name { get; set; }
     public Contract SignedContract { get; set; }

     public Client(String name, Contract contract)
     {
         Name = name;
         SignedContract = contract;
     }

     public override string ToString()
     {
         return "Client " + Name;
     }
 }

A few sample datas to make a demo work (called in the formLoad event of the windows form)

  Contract c1 = new Contract("NRCONTRACT0001");
  Contract c2 = new Contract("NRCONTRACT0005");
  Contract c3 = new Contract("NCAB_84_PK65");

  Client cl1 = new Client("BTHOS", c1);
  Client cl2 = new Client("FTIA Consulting", c2);
  Client cl3 = new Client("GAMMA INFO", c3);

  Client[] clients = new Client[] {cl1,cl2,cl3};
  Contract[] contracts = new Contract[] {c1, c2, c3};

  comboBox1.Items.AddRange(clients);
  comboBox2.Items.AddRange(contracts);

Then in the first combox box select index changed event, I pick up the object and cast it into a Client in order to take advantage of the relation between client and contract

  private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
  {
        comboBox2.SelectedItem = ((Client)comboBox1.SelectedItem).SignedContract;
  }

It works fine.

score 0 · Answer 6 · answered Nov 09 '16 at 04:40

    private DataSet m_ds = new DataSet();
    private CurrencyManager m_Currency;

    private void Form8_Load(object sender, EventArgs e)
    {
        DataTable T1 = m_ds.Tables.Add("T1");
        T1.Columns.Add("T"); 
        T1.Columns.Add("V");

        DataRow T1_ROW = T1.NewRow();
        T1_ROW["T"] = "1";
        T1_ROW["V"] = "1";
        T1.Rows.Add(T1_ROW);

        T1_ROW = T1.NewRow();
        T1_ROW["T"] = "2";
        T1_ROW["V"] = "2";
        T1.Rows.Add(T1_ROW);

        T1_ROW = T1.NewRow();
        T1_ROW["T"] = "3";
        T1_ROW["V"] = "3";
        T1.Rows.Add(T1_ROW);

        T1_ROW = T1.NewRow();
        T1_ROW["T"] = "4";
        T1_ROW["V"] = "4";
        T1.Rows.Add(T1_ROW);

        comboBox1.DataSource = T1;
        comboBox1.DisplayMember = "T";
        comboBox1.ValueMember = "V";

        m_Currency = this.BindingContext[m_ds, "T1"] as CurrencyManager;

        DataTable T2 = m_ds.Tables.Add("T2");
        T2.Columns.Add("ID");
        T2.Columns.Add("T");
        T2.Columns.Add("V");

        DataRow T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "1";
        T2_ROW["T"] = "1-1";
        T2_ROW["V"] = "1-1";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "1";
        T2_ROW["T"] = "1-2";
        T2_ROW["V"] = "1-2";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "1";
        T2_ROW["T"] = "1-3";
        T2_ROW["V"] = "1-3";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "1";
        T2_ROW["T"] = "1-4";
        T2_ROW["V"] = "1-4";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "2";
        T2_ROW["T"] = "2-1";
        T2_ROW["V"] = "2-1";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "2";
        T2_ROW["T"] = "2-2";
        T2_ROW["V"] = "2-2";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "2";
        T2_ROW["T"] = "2-3";
        T2_ROW["V"] = "2-3";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "2";
        T2_ROW["T"] = "2-4";
        T2_ROW["V"] = "2-4";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "3";
        T2_ROW["T"] = "3-1";
        T2_ROW["V"] = "3-1";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "3";
        T2_ROW["T"] = "3-2";
        T2_ROW["V"] = "3-2";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "3";
        T2_ROW["T"] = "3-3";
        T2_ROW["V"] = "3-3";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "3";
        T2_ROW["T"] = "3-4";
        T2_ROW["V"] = "3-4";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "4";
        T2_ROW["T"] = "4-1";
        T2_ROW["V"] = "4-1";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "4";
        T2_ROW["T"] = "4-2";
        T2_ROW["V"] = "4-2";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "4";
        T2_ROW["T"] = "4-3";
        T2_ROW["V"] = "4-3";
        T2.Rows.Add(T2_ROW);

        T2_ROW = T2.NewRow();
        T2_ROW["ID"] = "4";
        T2_ROW["T"] = "4-4";
        T2_ROW["V"] = "4-4";
        T2.Rows.Add(T2_ROW);

        System.Data.DataColumn T1_V = null;
        System.Data.DataColumn T2_V = null;
        T1_V = m_ds.Tables["T1"].Columns["V"];
        T2_V = m_ds.Tables["T2"].Columns["ID"];
        System.Data.DataRelation REL = new DataRelation("COM_ID", T1_V, T2_V);
        m_ds.Relations.Add(REL);

        comboBox2.DataSource = m_ds;
        comboBox2.DisplayMember = "T1.COM_ID.T";
        comboBox2.DisplayMember = "T1.COM_ID.V";
    }

    private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        DataRow[] Rows = m_ds.Tables["T1"].Select("V = '" + Convert.ToString(comboBox1.SelectedValue) + "'");
        if (Rows.Count() < 1)
            return;

        m_Currency.Position = m_ds.Tables["T1"].Rows.IndexOf(Rows[0]);
    }

It is first combobox selectedindex change event, second change currency manager position, therd chage relation member in table, final chage second combobx list — dongsik um, Nov 09 '16 at 04:58

score 0 · Answer 7 · edited Sep 02 '19 at 08:12

0

Shaibu , I know too late for it but it maybe will help someone just add this line code cmbDevice1.Items.Clear(); before this line cmbDevice1.Items.Add(myReader2[""]);

edited Sep 02 '19 at 08:12

Hasta Dhana

4,699
7
17
26

answered Sep 07 '18 at 20:46

Ardalan Husin

3
4

how to create relationship between two combo box in c# winform application

7 Answers7