How do i raise an event in a usercontrol and catch

问题:

I have a UserControl, and I need to notify the parent page that a button in the UserControl was clicked. How do I raise an event in the UserControl and catch it on the Main page? I tried using static, and many suggested me to go for events!

回答1:

Check out Event Bubbling -- http://msdn.microsoft.com/en-us/library/aa719644%28vs.71%29.aspx

Edit to add a quick example: (and additional edit to improve formatting)

User Control

public event EventHandler StatusUpdated;

private void FunctionThatRaisesEvent()
{
    //Null check makes sure the main page is attached to the event
    if (this.StatusUpdated != null)
       this.StatusUpdated(this, new EventArgs());
}

Main Page/Form

public void MyApp()
{
     //USERCONTROL = your control with the StatusUpdated event
     this.USERCONTROL.StatusUpdated += new EventHandler(MyEventHandlerFunction_StatusUpdated);
}

public void MyEventHandlerFunction_StatusUpdated(object sender, EventArgs e)
{
         //your code here
}

回答2:

Just add an event in your control:

public event EventHandler SomethingHappened;

and raise it when you want to notify the parent:

if(SomethingHappened != null) SomethingHappened(this, new EventArgs);

If you need custom EventArgs try EventHandler<T> instead with T beeing a type derived from EventArgs.

回答3:

Or if you are looking for a more decoupled solution you can use a messenger publisher / subscriber model such as MVVM Light Messenger here