How do I populate DropDownList with database data in C# windows application

Same as asp.net You can use Form_load Event to call any event.


for quick reference visit
http://www.daveoncsharp.com/2009/11/binding-a-windows-forms-combobox-in-csharp/[^]

first remove

if (!IsPostBack)

there is not post back in windows application.

then call your dropdownlist/combobox populate method at Form_Load() event. for an example...

private void Form1_Load(object sender, System.EventArgs e)
    {
Paraqit_ddListKlasa();
    }

you found if (!IsPostBack) in Windows application. strange...

for binding combobox in windows application you can use like this:-

using (SqlConnection cnn = new SqlConnection(connString))
{
    cnn.Open();
    using (SqlDataAdapter sda = new SqlDataAdapater("Select  KlasaViti, ID_Klasa from KLASA", cnn))
    {
        DataTable dt = new DataTable();
        sda.Fill(dt);

        comboBox.ValueMember = "ID";
        comboBox.DisplayMember = "KlasaViti";
        comboBox.DataSource = dt;
    }
}

in winform use ComboBox Control and also you need to use DisplayMember and ValueMember properties. call below method in form load event ( don't check for IsPostBack, it is not available in winform)
No need to call DataBind method like in web application

public void Paraqit_ddListKlasa()
{
    DataTable dt = new DataTable();
    SqlConnection sqlConn = new SqlConnection(StringKoneksioni.Stringu);
    sqlConn.Open();

    string SQLstringu = "Select  KlasaViti, ID_Klasa from KLASA ";
    SqlCommand cmd = new SqlCommand(SQLstringu, sqlConn);
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    da.Fill(dt);
    DataRow dataRow = dt.NewRow();
    dt["KlasaViti"] = "--Zgjedh--";
    dt.Rows.InsertAt(dataRow, 0);
    comboBox1.DataSource = dt;
    comboBox1.DisplayMember= "KlasaViti";
    comboBox1.ValueMember  = "ID_Klasa";

    sqlConn.Close();
}

Hello dr_iton,

There is no need of this code :

if (!IsPostBack)
          {
              Paraqit_ddListKlasa();
          }

In windows base application you need to write code in form_load event.

public void Paraqit_ddListKlasa()
        {
            DataTable dt = new DataTable();
            SqlConnection sqlConn = new SqlConnection(StringKoneksioni.Stringu);
            sqlConn.Open();
 
            string SQLstringu = "Select  KlasaViti, ID_Klasa from KLASA ";
            SqlCommand cmd = new SqlCommand(SQLstringu, sqlConn);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(dt);
 
            ddListKlasa.DataSource = dt;
            ddListKlasa.DataTextField = "KlasaViti";
            ddListKlasa.DataValueField = "ID_Klasa";
            ddListKlasa.DataBind();
            ddListKlasa.Items.Insert(0, new ListItem("--Zgjedh--", "0"));
            sqlConn.Close();
        }

call your method in form_load event like this :

Paraqit_ddListKlasa();

Other Idea:
-----------

1. Always try to create DAL (Data Access Layer) that you can use in WEB and WINDOWS FORM application as well.

Let me know if you have any further query.
Please, go through above link.
If its your answer, please mark as solution.
Best of luck for hunting solutions.

Thank you.
Regards,

Manoj Kalla

Hello friend, first of all there is no PostBack concept in Windows Application. Please remove the check from the following code:

//This check is meaningless in Windows App
if (!IsPostBack)
{

}

Let me know if you have any other query.

- DD