列表框和数据源-防止选择第一项 [英] ListBox and Datasource - prevent first item from being selected

问题描述

嘿.我有以下代码填充了我的列表框

Hey. I've got the following code that populates my list box

UsersListBox.DataSource = GrpList;

但是，在填充该框之后，默认情况下会选择列表中的第一项，并且会触发所选索引已更改"事件.如何防止在填充列表框后立即选择该项目，或者如何防止触发该事件?

However, after the box is populated, the first item in the list is selected by default and the "selected index changed" event fires. How do I prevent the item from being selected right after the list box was populated, or how do I prevent the event from firing?

谢谢

推荐答案

为避免触发事件，这是我过去使用的两个选项:

To keep the event from firing, here are two options I have used in the past:

1. 在设置数据源时注销事件处理程序.

1. Unregister the event handler while setting the DataSource.

UsersListBox.SelectedIndexChanged -= UsersListBox_SelectedIndexChanged;
UsersListBox.DataSource = GrpList;
UsersListBox.SelectedIndex = -1; // This optional line keeps the first item from being selected.
UsersListBox.SelectedIndexChanged += UsersListBox_SelectedIndexChanged;

创建一个布尔值标志以忽略该事件.

Create a boolean flag to ignore the event.

private bool ignoreSelectedIndexChanged;
private void UsersListBox_SelectedIndexChanged(object sender, EventArgs e)
{
    if (ignoreSelectedIndexChanged) return;
    ...
}
...
ignoreSelectedIndexChanged = true;
UsersListBox.DataSource = GrpList;
UsersListBox.SelectedIndex = -1; // This optional line keeps the first item from being selected.
ignoreSelectedIndexChanged = false;

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