How to call WCF Data Service Asynchronously (async Mode) using ASP.Net Callbacks

We can use ASP.Net Client Callbacks to invoke Data Service in Asynchronous mode without freezing the UI .

Download Sample Code

Alternative Titles

Async ASP.Net and WCF Data Service 

Instrucutions Step By Step

• Must read MSDN article http://msdn.microsoft.com/en-us/library/ms178208.aspx  before trying this sample
• Create a sample empty ASP.Net wesite (Not Web application)
• Copy all the files to website directory provided in this sample download 
• Add a service refernace to your project for Northwid Public OData service http://services.odata.org/Northwind/Northwind.svc/
• Locate the function "public void RaiseCallbackEvent(String eventArgument)" and replace with below mentioned code 

C#

 public void RaiseCallbackEvent(String eventArgument) 
    { 
        returnValue = "Result from Async Northwind Serice Call"+Environment.NewLine; 
        NorthwindEntities nwEntities =  
            new NorthwindEntities(new Uri("http://services.odata.org/Northwind/Northwind.svc/")); 
         
        foreach (Product item in nwEntities.Products) 
        { 
            returnValue = returnValue + String.Format("ProductID={0} ProductName={1} Price={2}",  
                item.ProductID, item.ProductName, item.UnitPrice) + Environment.NewLine; 
                 
        } 
        
    }

Run your application and navigate to http://localhost:22438/WebSite1/ClientCallback.aspx

How Does It Work 

• Actaually function LookUpStock() raise an Async call to server 
• Call is Routed to ' public void RaiseCallbackEvent(String eventArgument)"
• This function actually raise a query to Northwind Database and build an string with list of product 
• This list is returned to server using client call back " public String GetCallbackResult()"

Note : Based on data it may take long time to the result to be appered on UI

This code sample is create to support forum post http://social.msdn.microsoft.com/Forums/en-US/adodotnetdataservices/thread/d31c582d-0fba-4f1f-9573-49d05a199f1f