添加新项目之前，请检查列表框

问题描述

我想检查的项目尚不在列表框中存在之前，我添加新的项目。

I am trying to check that an item doesn't already exist in a list box before I add the new item.

            if (TeamNameTextBox.Text != "")
        {
            if (TeamNameListBox.Items.FindByValue(TeamNameListBox.Text) == null)
            {
                TeamNameListBox.Items.Add(TeamNameTextBox.Text);
                TeamNameTextBox.Text = "";

                int teamCountUpdate = TeamNameListBox.Items.Count;
                if (teamCountUpdate == 1)
                {
                    TeamCount.Text = teamCountUpdate.ToString() + " Team";
                }
                else
                {
                    TeamCount.Text = teamCountUpdate.ToString() + " Teams";
                }
            }
            else
            {
                AddTeamSeasonError.Text = "This team has already been added";
            }
        }
        else
        {
            AddTeamSeasonError.Text = "Please select a team";
        }

我已经得到它来检查，​​如果文本框为空，但我需要检查用户尝试添加的项目是不是已经在列表框中。

I have got it to check if the text box is blank, but I need to check that the item a user is trying to add is not already in the the list box.

我已经试过行：

if (TeamNameListBox.Items.FindByValue(TeamNameListBox.Text) == null)

但是，这并不工作，我如何能做到检查有什么建议？

But that doesn't work, any suggestions on how I can do the check?

推荐答案

觉得你至少应该尝试使用 TeamNameTextBox 而不是 TeamNameListBox 作为参数

think you should at least try to use TeamNameTextBox instead of TeamNameListBox as argument

if (TeamNameListBox.Items.FindByValue(TeamNameTextBox.Text) == null)

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