wpf 如何删除动态创建的事件处理程序？
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How to remove event handler which is dynamically created?
提问by butaro
I am relatively newbie. The problem I have is a simple one I think, but I cant find a solution. Clicking on button1 opens a popup and adds to canvas1a MouseDown event handler canvas1.MouseDown += (s1, e1) =>{...};I want to remove this when the user closes the popup. Here's the whole code:
我是比较新手。我的问题是我认为的一个简单问题，但我找不到解决方案。单击 button1 会打开一个弹出窗口并添加到canvas1MouseDown 事件处理程序中，canvas1.MouseDown += (s1, e1) =>{...};我想在用户关闭弹出窗口时将其删除。这是整个代码：
namespace MyfApplication1
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
int linesNumber = 0;
Button button1 = new Button();
button1.Content = "Draw";
button1.HorizontalAlignment = HorizontalAlignment.Left;
button1.VerticalAlignment = VerticalAlignment.Top;
button1.Click += (s, e) =>
{
Popup popup = new Popup();
popup.PlacementTarget = button1;
popup.IsOpen = true;
Button closePopupButton = new Button();
closePopupButton.Content = "close";
closePopupButton.Click += (s1, e1) =>
{
popup.IsOpen = false;
// remove canvas1.MouseDown event handler here
};
popup.Child = closePopupButton;
canvas1.MouseDown += (s1, e1) =>
{
Point point = Mouse.GetPosition(canvas1);
Line line = new Line();
line.X2 = point.X; line.Y2 = point.Y;
line.Stroke = Brushes.Red; line.StrokeThickness = 1;
canvas1.Children.Add(line);
linesNumber++;
};
};
grid1.Children.Add(button1);
}
}
}
回答by doerig
save the eventhandler somewhere in a variable
将事件处理程序保存在变量中的某处
MouseButtonEventHandler onMousedown = (o, args) =>
{
...
};
canvas1.MouseDown += onMouseDown;
and later you can remove the eventhandler again:
稍后您可以再次删除事件处理程序：
canvas1.MouseDown -= onMouseDown;
