Question

我编写代码文本框以添加列表框值。我想为重复添加提供显示错误，但这不起作用。有人可以帮忙吗？

protected void btnAdd_Click(object sender, EventArgs e)
                {
                  AddToList();
                  lstValue.Items.Remove("");
                }

private void AddToList()
    {
      if (lstValue.Items.Count > 0)
      {
        txtQlt.Text = txtQlt.Text + "," + cmbQualityRef.SelectedItem.ToString();
      }
      else
      {
        txtQlt.Text = cmbQualityRef.SelectedItem.ToString();
      }

      ListItem itm = new ListItem();
      itm.Value = cmbQualityRef.SelectedValue;
      itm.Text = cmbQualityRef.SelectedItem.ToString();
      if (itm != null)
      {
        lblMsg.Text = "Selected Item Already Exists In The List.";
        return;
      }
      lstValue.Items.Add(itm);
      lstValue.Items.Remove("");

    }

Answer 1

您可以使用items.Contains并检查字符串。这是通过分配itm值和降低你的功能。

private void AddToList()
{

  if (lstValue.Items.FindByText(cmbQualityRef.SelectedItem.ToString()) == null)
  {
    if (lstValue.Items.Count > 0)
    {
       txtQlt.Text = txtQlt.Text + "," + cmbQualityRef.SelectedItem.ToString();
    }
    else
    {
       txtQlt.Text = cmbQualityRef.SelectedItem.ToString();
    }
   ListItem itm = new ListItem();
   itm.Value = cmbQualityRef.SelectedValue;
   itm.Text = cmbQualityRef.SelectedItem.ToString();

   lstValue.Items.Add(itm);
  }
  else
  {
     lblMsg.Text = "Selected Item Already Exists In The List.";
  }
}

Answer 2

使用以下代码示例检查列表

 private void AddToList()
    {
        if (lstValue.Items.Count > 0)
        {
            txtQlt.Text = txtQlt.Text + "," + cmbQualityRef.SelectedItem.ToString();
        }
        else
        {
            txtQlt.Text = cmbQualityRef.SelectedItem.ToString();
        }



        if (lstValue.Items.FindByText(txtQlt.Text.ToString()) != null)
        {
            //record is present in list and you code for msg
            lblMsg.Text = "Selected Item Already Exists In The List.";
            return;
        }
        else
        {

            ListItem itm = new ListItem();
            itm.Value = cmbQualityRef.SelectedValue;
            itm.Text = cmbQualityRef.SelectedItem.ToString();                
            lstValue.Items.Add(itm);
            lstValue.Items.Remove("");
        }



    }

其中lstValue是ListBox的id

给出错误消息，文本框中的重复值以添加ListBox值

2 个答案: