Question

我正在开发一个我正在使用comboBox和ListView的应用程序。我想在启动应用程序时从数据库中显示Listview中的记录。并且combBox用于过滤以在comViewBox指定的ListView中显示那些记录。问题是，当我启动我的应用程序时，它不会在ListView中显示任何内容（comboBox和ListView都是从数据库填充的）。虽然填充了comboBox，但未填充ListView。当我在comboBox中选择一个项目时，它会在listView中显示这些数据。我为dataBase连接使用了一个单独的类。我的代码如下。

private void EmployeeAttendence_Load(object sender, EventArgs e)
        {
            try
            {
                table = dbOperation.select("employs.emp_id, employs.emp_name, employs.emp_fname, designation.name from employs inner join designation on designation.id = employs.designation");
                listView1.Items.Clear();
                foreach (DataRow row in table.Rows)
                {
                    listView1.Items.Add(row[0].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[1].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[2].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[3].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add("P");
                }

                table = dbOperation.select("* from designation");
                comboBox1.Items.Clear();
                comboBox1.DataSource = table;
                comboBox1.DisplayMember = "name";
                comboBox1.ValueMember = "id";
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

这是comboBox过滤编码。

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {

            try
            {
                table = dbOperation.select("employs.emp_id, employs.emp_name, employs.emp_fname, designation.name from employs inner join designation on designation.id = employs.designation where employs.designation = '" + comboBox1.SelectedValue + "'");

                listView1.Items.Clear();
                foreach (DataRow row in table.Rows)
                {
                    listView1.Items.Add(row[0].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[1].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[2].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[3].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add("P");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }

        }

这是我的数据库选择查询编码。

public DataTable select(string table_name)
        {
            table = new DataTable();
            command.CommandText = "select " + table_name;
            command.Connection = con;
            con.Open();
            adapter.SelectCommand = command;
            adapter.Fill(table);
            con.Close();
            return table;
        }

Answer 1

我认为您正在使用Windows窗体...

我认为问题在于，当您第一次加载winform时，您希望使用组合框的第一项填充列表框

因此，在form_load事件中，您应该在组合框中选择索引

private void EmployeeAttendence_Load(object sender, EventArgs e)
{
    try
    {
        table = dbOperation.select("employs.emp_id, employs.emp_name, employs.emp_fname, designation.name from employs inner join designation on designation.id = employs.designation");
        listView1.Items.Clear();
        foreach (DataRow row in table.Rows)
        {
            listView1.Items.Add(row[0].ToString());
            listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[1].ToString());
            listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[2].ToString());
            listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[3].ToString());
            listView1.Items[listView1.Items.Count - 1].SubItems.Add("P");
        }

        table = dbOperation.select("* from designation");
        comboBox1.Items.Clear();
        comboBox1.DataSource = table;
        comboBox1.DisplayMember = "name";
        comboBox1.ValueMember = "id";

        comboBox1.SelectedIndex = 0; //this should raise the event comboBox1_SelectedIndexChanged(object sender, EventArgs e) and the listbox will be populated

     }
     catch (Exception ex)
     {
        MessageBox.Show(ex.ToString());
     }
}

Answer 2

尝试在Page_Load事件

中添加if(!Page.IsPostBack)

    private void EmployeeAttendence_Load(object sender, EventArgs e)
    {
        if(!Page.IsPostBack)
        {
          try
          {
              table = dbOperation.select("employs.emp_id, employs.emp_name, employs.emp_fname, designation.name from employs inner join designation on designation.id = employs.designation");
              listView1.Items.Clear();
              foreach (DataRow row in table.Rows)
              {
                listView1.Items.Add(row[0].ToString());
                listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[1].ToString());
                listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[2].ToString());
                listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[3].ToString());
                listView1.Items[listView1.Items.Count - 1].SubItems.Add("P");
              }

              table = dbOperation.select("* from designation");
              comboBox1.Items.Clear();
              comboBox1.DataSource = table;
              comboBox1.DisplayMember = "name";
              comboBox1.ValueMember = "id";
          }
          catch (Exception ex)
          {
             MessageBox.Show(ex.ToString());
          }
        }
    }

在OnLoad函数中填充listview

2 个答案:

尝试在Page_Load事件