Sharepoint 2010 : Creating a Pluggable Workflow Service (part 6) - Calling a SharePoint-Hosted WCF Service

3. Calling a SharePoint-Hosted WCF Service

To complete our calculation engine implementation, we need to add some code to our DemoCalculationEngine project. We need a method that can make a call into our SharePoint WCF service to notify the workflow that calculation is complete. With the SharePoint project deployed, we first need to add a service reference to the SharePoint WCF service.

1. In the DemoCalculationEngine project, choose Project | Add Service Reference. Set the Address to http://localhost/_layouts/WorkflowDemonstration/CalculationResultService.svc.

2. Since the service is hosted within SharePoint, requests must be authenticated; as a result, we need to enter credentials for a user account with permissions to connect to the SharePoint site.

3. Once the service metadata has been retrieved, set the Namespace to CalculationResultService and the click OK to complete the process.

   Note

   When adding a service reference for a SharePoint, you’ll sometimes see multiple prompts to enter credentials. Usually, after entering valid credentials once, clicking Cancel on subsequent prompts will allow the process to continue.

   
   

4. With our service reference in place, we can move on to add the following code to handle the button click event in Form1.cs:

   private void button1_Click(object sender, System.EventArgs e)
       {
         foreach (DataGridViewRow row in dataGridView1.SelectedRows)
         {
           CalculationResultService.CalculationResultServiceClient client = new
                        CalculationResultService.CalculationResultServiceClient();
           client.ClientCredentials.Windows.AllowedImpersonationLevel =
                  System.Security.Principal.TokenImpersonationLevel.Impersonation;
           CalculationResultService.CalculationResult result = new
                                   CalculationResultService.CalculationResult();
   
           CalculationRequest selected = row.DataBoundItem as CalculationRequest;
   
           result.Result = selected.ProductName + " Complete";
           result.InstanceId = selected.InstanceId;
           result.SiteId = selected.SiteId;
           result.WebId = selected.WebId;
   
           if (client.ProcessCalculationResult(result))
           {
             row.Selected = false;
             _calculationList.Remove(selected);
           }
         }
       }
   
   
   					  

We can now manually trigger calculation results by selecting an item from the data grid and then clicking the Send Result button.

Tip

When hosting WCF services in SharePoint, it’s important that the client proxy allows impersonation; otherwise, some weird and wonderful COM errors may be thrown by SharePoint. To allow impersonation, set the AllowedImpersonationLevel to Impersonation, as shown in the preceding code sample.