检查事件已存在 [英] Check if an event already exists

问题描述

我有一个数据网格加载行事件

I have a data grid loading row event

_gridObj.LoadingRow += new EventHandler<DataGridRowEventArgs>(_gridObj_LoadingRow);

和在处理程序中，我创建另一个事件。在下面的代码我怎么能知道是否MouseLeftBtn事件已存在该行？

and in the handler I am creating another event. In the following code how can I know if the MouseLeftBtn event already exists for that row?

void _gridObj_LoadingRow(object sender, DataGridRowEventArgs e)
{
    e.Row.MouseLeftButtonUp += new MouseButtonEventHandler(Row_MouseLeftButtonUp);
}

谢谢，

Thanks,

巫毒

推荐答案

根据您的意见，你不希望在这种情况下，我再重新订阅退订附加muliple处理程序。它不给一个错误，如果不存在，并确保只有一个处理退订。

Based on your comment that you don't want to attach muliple handlers in this case I unsubscribe then resubscribe. It does not give an error unsubscribing if none exists and ensures only one handler.

void _gridObj_LoadingRow(object sender, DataGridRowEventArgs e)
{
    e.Row.MouseLeftButtonUp -= new MouseButtonEventHandler(Row_MouseLeftButtonUp);
    e.Row.MouseLeftButtonUp += new MouseButtonEventHandler(Row_MouseLeftButtonUp);
}

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