How do I pass objects in EventArgs

c#, eventargs

Solution

You would have to declare your event using `EventHandler<T>` where `T` is your class that derives from `EventArgs`:

public event EventHandler<LoginCompletedEventArgs> LoginCompleted;

`LoginCompletedEventArgs` could look like this:

public class LoginCompletedEventArgs : EventArgs
{
    private readonly YourBusinessObject _businessObject;

    public LoginCompletedEventArgs(YourBusinessObject businessObject)
    {
        _businessObject = businessObject;
    }

    public YourBusinessObject BusinessObject
    {
        get { return _businessObject; }
    }
}

Usage would be like this:

private void RaiseLoginCompleted(YourBusinessObject  businessObject)
{
    var handler = LoginCompleted;
    if(handler == null)
        return;

    handler(this, new LoginCompletedEventArgs(businessObject));
}

Please notice how I implemented `RaiseLoginCompleted`. This is a thread-safe version of raising the event. I eliminates a possible `NullReferenceException` that can occur in a race condition scenario where one thread wants to raise the event and another thread un-subscribes the last handler after the `if` check but before actually invoking the handler.

Problem

I have a usercontrol that raises an event after communicating with a web service. The parent handles this event when raised. What I thought would be the proper approach would be to pass the object returned from the webservice to the parent as eventargs??? If this is the proper way I can't seem to find the instructions on how to do so. UserControl ``` public event EventHandler LoginCompleted; ``` then later after the service returns biz object: ``` if (this.LoginCompleted != null) { // This is where I would attach / pass my biz object no? this.LoginCompleted(this, new EventArgs()); } ``` Parent ``` ctrl_Login.LoginCompleted += ctrl_Login_LoginCompleted; ....snip.... void ctrl_Login_LoginCompleted(object sender, EventArgs e) { // Get my object returned by login } ``` So my question is what would be the "approved" method for getting the user object back to the parent? Create a property class that everything can access and put it there?

Original source