c# - 在添加新项目之前检查 ListBox

Question

在添加新项目之前，我正在尝试检查列表框中是否不存在该项目。

            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";
        }

我有它来检查文本框是否为空白，但我需要检查用户尝试添加的项目是否不在列表框中。

我试过这条线：

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

但这不起作用，关于如何进行检查的任何建议？

Answer 1

if (!string.IsNullOrEmpty(TeamNameTextBox.Text))
{
    if (!TeamNameListBox.Items.Contains(TeamNameTextBox.Text))
    {
        TeamNameListBox.Items.Add(TeamNameTextBox.Text);
    }
    else
    {
        // item already exists in listbox
    }
}
else
{
    // textbox is empty
}