How to refresh combobox winform c#

Question

i create winform with c# that had two combobox

The form look like this

combobox1 select company from database

combobox2 select project from database depend on company from combobox1

everything ok when the form loaded but i want to refresh combobox2 when i change company in combobox1

this is my code

using System;
using System.Data;
using System.Windows.Forms;
using Oracle.ManagedDataAccess.Client;

namespace WindowsFormsApp3
{
    public partial class Form_AC071503 : Form
    {
        public Form_AC071503()
        {
            InitializeComponent();
        }

        DataSet ds = new DataSet();

        OracleCommand cmd1;
        OracleDataAdapter da1;

        OracleCommand cmd2;
        OracleDataAdapter da2;

        private void Form_AC071503_Load(object sender, EventArgs e)
        {
            cmd1 = new OracleCommand("SELECT company,company_name from COMPANIES", Class_All.Connection);
            da1 = new OracleDataAdapter(cmd1);
            da1.Fill(ds, "COMPANIES");
            input_company.DataSource = ds.Tables["COMPANIES"];
            input_company.DisplayMember = "company_name";
            input_company.ValueMember = "company";

            cmd2 = new OracleCommand("SELECT project,project_name from PROJECTS where COMPANY = '" + input_company.SelectedValue.ToString() + "'", Class_All.Connection);
            da2 = new OracleDataAdapter(cmd2);
            da2.Fill(ds, "PROJECTS");
            input_project.DataSource = ds.Tables["PROJECTS"];
            input_project.DisplayMember = "project_name";
            input_project.ValueMember = "project";
        }

        private void Input_company_SelectedIndexChanged(object sender, EventArgs e)
        {
            /*i try to use the same code in Form_AC071503_Load like this

              cmd2 = new OracleCommand("SELECT project,project_name from PROJECTS where COMPANY = '" + input_company.SelectedValue.ToString() + "'", Class_All.Connection);
              da2 = new OracleDataAdapter(cmd2);
              da2.Fill(ds, "PROJECTS");
              input_project.DataSource = ds.Tables["PROJECTS"];
              input_project.DisplayMember = "project_name";
              input_project.ValueMember = "project";

              but not work because the list project not refresh but increased with new value*/ 
        }
    }
}

thank you in advice.

Answer 1

您需要在combobox1中添加ValueChanged事件。