Using exception handling scope to handle errors in client object model : SharePoint 2010

While using client object model in SharePoint 2010, many a times we come across situations where in we call the
ctx.ExecuteQuery() method and some error occurs on the server due to which we get a 'ServerException' which does not give us the opportunity to make corrections in the operation that we are trying to do.

The ExceptionHandlingScope class models a try/catch behaviour for such situations.When we add the code within this scope,it is processed as if its present in a try/catch and gives the opportunity to correct the error in the catch/finally block.

For eg. lets take an example where in we are trying to update the description of a list using managed client object model.If the list does not exist in the target site, it will throw an exception.Now, in the catch block of the exception handling scope , we can create the list in the site and then update its description.

The code below demonstrates this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using Microsoft.SharePoint.Client;

namespace Sharepoint2010TestConsoleApp

{

    class Program

    {

        static void Main(string[] args)

        {

           using (ClientContext ctx = new ClientContext("http://br-pc-341:2222"))

            {

                //Set up error handling

                ExceptionHandlingScope xScope = new ExceptionHandlingScope(ctx);

                using (xScope.StartScope())

                 {

                    using (xScope.StartTry())

                    {

                        //Try to update the description of a list named "Test List"

                        List testList = ctx.Web.Lists.GetByTitle("Test List");

                        testList.Description = "Test List Description";

                        testList.Update();

                    }

                    using (xScope.StartCatch())

                    {

                        //Fails if the list "Test List" does not exist

                        //So, we'll create a new list

                        ListCreationInformation testListCI = new ListCreationInformation();

                        testListCI.Title = "Test List";

                        testListCI.TemplateType = (int)ListTemplateType.GenericList;

                        testListCI.QuickLaunchOption = Microsoft.SharePoint.Client.QuickLaunchOptions.On;

                        List list = ctx.Web.Lists.Add(testListCI);

                    }

                    using (xScope.StartFinally())

                    {

                        //Try to update the list now if it failed originally

                        List testList = ctx.Web.Lists.GetByTitle("Test List");

                        if (testList.Description.Length == 0)

                        {

                            testList.Description = "Test List Description";

                            testList.Update();

                        }

                    }

                }

                //Execute the entire try-catch as a batch!

                ctx.ExecuteQuery();

                Console.WriteLine("Description Updated !!");

            }

        }

    }

}

This console application updates the description of the list named 'Test List'. If the list does not exist , the list is
created in the catch block and then the description is updated.

The list with the updated description can be seen on the sharepoint site: