Question

I have a challenge in my C# .NET application that I can’t figure out how to resolve. I have an object that has a method called “Load”. If the object is loaded successfully, one event is fired. If the object fails to load, another event is fired. This entity is defined as follows:

public class MyEntity
{
  public event EventHandler Load_Succeeded;
  public event EventHandler Load_Failed;
  public void Load()
  {
    /*
     Asynchronously load the entity code here.
    */
  }

  private void Load_Completed(IAsyncResult result)
  {
    // Fire Load_Succeeded or Load_Failed
  }
}

Now, if the Load fails, I store the object in isolated storage to attempt to load it later. When I attempt to load the object later, I have the following code:

MyEntity myEntity = GetFromIsolatedStorage();
myEntity.Load_Failed -= new EventHandler(myEntity_Load_Failed);
myEntity.Load_Failed += new EventHandler(myEntity_Load_Failed);

myEntity.Load_Succeeded -= new EventHandler(myEntity_Load_Succeeded);
myEntity.Load_Succeeded += new EventHandler(myEntity_Load_Succeeded);
myEntity.Load();

The odd part is, when I run the Load code via the entity loaded from isolated storage, the original Load_Failed and Load_Succeeded event handlers are executed. Even though I am using “-=”. What am i doing wrong? How do I clear all of the event handlers on an object so that I can essentially reset them?

Thank you!

Answer 1

You can remove an eventHandler only on the object that defines the event. That means you can use this:

    public class MyEntity
{
  public event EventHandler Load_Succeeded;
  public event EventHandler Load_Failed;
  public void Load()
  {
    /*
     Asynchronously load the entity code here.
    */
  }

  private void Load_Completed(IAsyncResult result)
  {
    // Fire Load_Succeeded or Load_Failed
  }

  public void ResetEvents()
  {
        this.Load_Succeeded = null;
        this.Load_Failed = null;
  }

}

And then just call

myEntity.ResetEvents();