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WCF Completed Event firing more than once

The problem situation is stated in the title. =P

The “fix” to the problem is something real simple. I didn’t notice it when it happened to me the first time. This post is also posted to remind myself about it.

This is an example of a code with the problem.

public class WorkingArea{
Server.ServiceClient client = new Server.ServiceClient();

public WorkingArea()

private void btnCheck_Click(object sender, RoutedEventArgs e)
client.CheckCompleted += new EventHandler(Client_UpdateCompleted);

This code seems to be working fine. I have a Service which I declare it as client and everytime I click on the button Check, i attach the event handler and call the async method to run it. But wait, what went wrong is this.
“…..everytime I click on the button Check, i attach the event handler and call…….”

What happen is there will be alot handlers being attached to the client variable as times go by ( with the user clicking the button in our example ). The callback/comepleted event will increasingly happen with the button click in this example. With abit of moving of that line where you attach the handler. This will solve the problem.
“client.CheckCompleted += new EventHandler(Client_UpdateCompleted);”

I will recommend putting this in the constructor, loaded event handler or onNaviagtedTo. This will depends on what is the architecture of the application you are building.

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