如何将组合框中的项目显示到列表框

Question

我正在开发一个window form 应用程序。我有一个comboBox 和一个listBox。在我的组合框中，我有 5 个项目，我想将我从组合框中选择的相应项目显示到列表框。

假设如果我选择第 1 项，它将显示第 1 项。如果我选​​择第 2 项，它将显示第 2 项，第 1 项将消失，反之亦然。到目前为止，我已经尝试过这段代码

listBox1.Items.Add(name)

这个ListBox add statment将新的item添加到listBox中，比如item1，item2，item3等等，这不是我想要的。

代码。

using System.IO;
using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello, World!");

           private void loadComboBox()
        {
            myConn = new SqlConnection("Server = localhost; Initial Catalog= dbName; Trusted_Connection = True");

            try
            {
                myConn.Open();
                string query = "select * from Application_Detail";

                myCommand = new SqlCommand(query, myConn);

                //myCommand.ExecuteNonQuery();
                //reading the value from the query
                SqlDataReader dr = myCommand.ExecuteReader();
                //Reading all the value one by one
                while (dr.Read())
                {
                    //column is 1 in Application_Detail Data
                    string name = dr.GetString(1);
                    applicationComboBox.Items.Add(name);
                }
                myConn.Close();
            }catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        private void fill_checkListBox()
        {
            myConn = new SqlConnection("Server = localhost; Initial Catalog= dbName; Trusted_Connection = True");

            try
            {
                myConn.Open();

                int index = applicationComboBox.SelectedIndex + 1;
                string query = " SELECT td.chineseName, ad.applicationId, aud.applicationId, ad.applicationName FROM[AppUser_Detail] as aud LEFT OUTER JOIN[Teacher_Detail] as td ON aud.teacherId = td.teacherId LEFT OUTER JOIN[Application_Detail] as ad ON aud.applicationId = ad.applicationId LEFT OUTER JOIN[Class_Detail] as cd ON aud.classId = cd.classId where aud.applicationId = '" + index + "' AND NOT(td.teacherId IS NULL AND cd.classId IS NULL)";
                myCommand = new SqlCommand(query, myConn);

                SqlDataReader dr = myCommand.ExecuteReader();

                //Reading all the value one by one
                while (dr.Read())
                {
                    //column is 1 in Application_Detail Data



                        //string value = applicationComboBox.GetItemText(applicationComboBox.Items[i]);
                        string name = dr.GetString(0);

teacherCheckListBox.Items.Clear();\更新了这行teacherCheckListBox.Items.Add(name);

                }
                //teacherCheckListBox.DataSource = dt;
                myConn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}

有什么想法吗？

Answer 1

   public Form1()
        {
            InitializeComponent();
            List<string> items = new List<string>();
            items.Add("sachin");
            items.Add("dravid");
            items.Add("ganguly");
            cmbSample.DataSource = items;
        }

        private void cmbSample_SelectedValueChanged(object sender, EventArgs e)
        {
            lstSample.Items.Clear();
            lstSample.Items.Add(cmbSample.SelectedItem);
            lstSample.SelectedItem = cmbSample.SelectedItem;
        }

Answer 2

您可以使用以下代码清除列表框并仅插入一项。

private void cmbSample_SelectedValueChanged(object sender, EventArgs e)
{
    lstSample.Items.Clear();
    lstSample.Items.Add(cmbSample.SelectedItem);
    lstSample.SelectedItem = cmbSample.SelectedItem;
}

但是这里lstSample.Items.Clear(); 会清除列表框中的任何内容。如果你不想这样，那么你可以避免这一行并继续其余两行，这将在现有列表框中插入一个新项目并选择新添加的项目。

private void cmbSample_SelectedValueChanged(object sender, EventArgs e)
{
    lstSample.Items.Add(cmbSample.SelectedItem);
    lstSample.SelectedItem = cmbSample.SelectedItem;
}