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tj62 View Drop Down
Groupie
Groupie
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Joined: 21-May-2009
Location: Iceland
Posts: 81 		Post Options Post Options   Quote tj62 Quote  Post ReplyReply Direct Link To This Post Topic: AsyncSerialTask
    Posted: 30-Sep-2009 at 7:53am

Hi,

I'm trying to use AsyncSerialTask with the  AddAsyncInvokeServerMethod(). However the declaration of this metod that the Intellisens shows looks like chinees to me. I could not find any DevForce documentation for this nor any samples. The documentation includes one sample for AsyncSerialTask with limited explanation...hard to understand.
 
Can anyone explain for me how to use AssyncSerialTask.Create().AddAsyncInvokServerMethod()
 
Here is the serial sequence I'm trying to move to AsyncSerialTask:
 
  private void LoadData(string userID) {
   Guid myToken = Guid.NewGuid();
   object[] param = {userID};
   m_mgr.InvokeServerMethodAsync("C2NetDomainModel.EntCustomer,C2NetDomainModel",
            "GetCustomerIDs",
            GotCustomerIDs, myToken, userID);
  }
  public void GotCustomerIDs( InvokeServerMethodEventArgs args )
  {
   if( args.Error != null )
    WriteMessage( args.Error.Message );
   else
   {
    int[] customerIDs = ((C2NetDomainModel.IntIDs)(args.Result)).p_ids;
    var customerQ = m_mgr.EntCustomerSet
           .OrderBy( c => c.p_name )
           .WhereIn( c => c.p_customerID , customerIDs );
    m_mgr.ExecuteQueryAsync( (IEntityQuery<EntCustomer>)customerQ, GotCustomers , null );
   }
  }
  private void GotCustomers(EntityFetchedEventArgs args)
  {
   if (args.Error != null) {
    WriteMessage(args.Error.Message);
   }
   else {
    //foreach( EntCustomer c in (System.Linq.IQueryable)args.Result )
    foreach( EntCustomer c in (IEnumerable<EntCustomer>)args.Result )
    {
     _customers.Add(c);
    }
    // Set CurrentItem to first Customer so form will flesh out
    if (_customers.Count > 0) {
     _customerDataForm.CurrentItem = _customers[0];
    }
    ReportFetchCount(args.Result, "Customer");
   }
  }

Can anyone tell me how to change this to a AsyncSerialTask?
 
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kimj View Drop Down
IdeaBlade
IdeaBlade
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Joined: 09-May-2007
Posts: 1391 		Post Options Post Options   Quote kimj Quote  Post ReplyReply Direct Link To This Post Posted: 30-Sep-2009 at 2:22pm
The syntax of the AsyncSerialTask is pretty abstruse.  Here's one way to implement this - 


 private void LoadData(string userID) {
   //Guid myToken = Guid.NewGuid();
   //object[] param = {userID};


   AsyncSerialTask.Create<string>()
        .AddAsyncInvokeServerMethod<object, object, InvokeServerMethodEventArgs>(m_mgr, 
  "C2NetDomainModel.EntCustomer,C2NetDomainModel", "GetCustomerIDs",
   inputArg=> new object[] {inputArg})
        .AddAsyncQuery(args => GotCustomerIds(args))
        .AddExceptionHandler(exArgs => WriteMessage(exArgs.Exception.Message))
        .Execute(userID, (completionArgs) => GotCustomers(completionArgs.Result));
  }


  public IEntityQuery<EntCustomer> GotCustomerIDs( InvokeServerMethodEventArgs args )
  {
    int[] customerIDs = ((C2NetDomainModel.IntIDs)(args.Result)).p_ids;
    var customerQ = m_mgr.EntCustomerSet
           .OrderBy( c => c.p_name )
           .WhereIn( c => c.p_customerID , customerIDs );


    return customerQ;
  }


  private void GotCustomers(EntityFetchedEventArgs<EntCustomer> args)
  {
    foreach( EntCustomer c in args.Result ) 
    {
     _customers.Add(c); 
    } 
    // Set CurrentItem to first Customer so form will flesh out 
    if (_customers.Count > 0) {
     _customerDataForm.CurrentItem = _customers[0];
    }
    ReportFetchCount(args.Result, "Customer");
  }
 
Things to note -
1) When you create the task you can specify the type of the input argument, in this case a string.
2) A few of the overloads for AddAsyncInvokeServerMethod take a lambda as a final argument.  This is what we're using here: it takes a string (the input to the task) and returns an object array containing that string.
3) AddAsyncInvokeServerMethod defines T0, T1 and T2 and I admit I don't know why there are 3 type arguments instead of two.  But anyway, T0 and T1 should be the input type (and can be 'object' if no input is provided, and T2 is 'InvokeServerMethodArgs'. 
4) Exceptions are handled a bit differently with an AsyncSerialTask, and you should add an exception handler to the task to trap any errors.
5) GotCustomerIDs takes the InvokeServerMethodEventArgs and builds a query, which it then returns as the async query to be run next.
6) task.Execute accepts an input argument, in this case the string userID.  This is passed to the first action in the task.
7) At completion, the results of the last action are available in the Result property.  This is passed to the GotCustomers method.
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