Service call queue

I am implementing a Silverlight application that makes heavy use of WCF services, now I have gotten to the point where sometimes there are several long service calls that block other service calls.

These service calls will eventually end. I would like to see if its a queue system that makes calls to a service one after the other, so long calls will hold other calls, but will not time out.

I am using service agents to transfer service calls

public interface IExampleServiceAgent
{
    void ProcessData(int a, string b, EventHandler<ProcessDataCompletedEventArgs> callback);
}


Public ExampleServiceAgent1 : IExampleServiceAgent
{
     ExampleClient _Client = new ExampleClient();

     public void ProcessData(int anInt, string aString, EventHandler<ProcessDataCompletedEventArgs> callback)
     {
           EventHandler<ProcessDataCompletedEventArgs> wrapper = null;
           wrapper = (a,b) =>
           {
               callback(a,b);
               _Client.ProcessDataCompleted -= wrapper;
           }
           _Client.ProcessDataCompleted += wrapper;
           _Client.ProcessDataAsync(anInt,aString);
     }
}

      

        
        
        
      

    

Then the above service agent will be called from the code like this:

ServiceAgent.ProcessData(1,"STRING", (a,b) =>
{
    if (b.Error != null)
    {
         //Handle Error
    }
    else
    { 
         //DO something with the data
    }
}

      

        
        
        
      

    

Is there a way that I could queue these service calls and execute them one by one?

I tried wrapping them as Actions and adding them to the queue, but that's not waiting for the execution to complete before starting the next one, and although they do call the service correctly, no data is returned to the calling ViewModel.