如何序列化Microsoft.SharePoint.Client.ListItem（Sharepoint-2013）？

Question

I want to create a WCF Service that returns the SharePoint ListCollection. I have tried by using following code:

public class Service1 : IService1
{
    public ListItemCollection GetList()
    {
        string username = "xxx";
        string userPassword ="xxx";
        var securePassword = new SecureString();
        for (int i = 0; i < userPassword.Length; i++)
        {
            securePassword.AppendChar(userPassword[i]);
        }
        var creds = new SharePointOnlineCredentials(username, securePassword);
        var clientContext = new ClientContext("MySharepointurl");
        clientContext.Credentials = creds;

        List announcementsList = clientContext.Web.Lists.GetByTitle("mylist");
        CamlQuery query = CamlQuery.CreateAllItemsQuery(100);
        var items = announcementsList.GetItems(query);
        clientContext.Load(items);
        clientContext.ExecuteQuery();

        return items;

    }

}

But it gives me error like follows:

Type 'Microsoft.SharePoint.Client.ListItem' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. If the type is a collection, consider marking it with the CollectionDataContractAttribute. See the Microsoft .NET Framework documentation for other supported types.

Answer 1

after searching lot i had come across my solution as follows if any one had same problem:

public List<MyClass> GetList()
    {
        try
        {
            string username = ConfigurationManager.AppSettings["username"];
            string password = ConfigurationManager.AppSettings["password"];
            string url = ConfigurationManager.AppSettings["AccountUrl"];
            var newList = new List<MyClass>();
            var securePassword = new SecureString();
            for (int i = 0; i < password.Length; i++)
            {
                securePassword.AppendChar(password[i]);
            }
            var creds = new SharePointOnlineCredentials(username, securePassword);
            var clientContext = new ClientContext(url)
            {
                Credentials = creds
            };

            List announcementsList = clientContext.Web.Lists.GetByTitle("mylist");
            CamlQuery query = CamlQuery.CreateAllItemsQuery();
            var items = announcementsList.GetItems(query);
            clientContext.Load(items);
            clientContext.ExecuteQuery();
            foreach (var col in items)
            {
                newList.Add(new MyClass()
                {
                    Id = Convert.ToInt32(col["ID"]),
                    FirstName = (string) col["FN"],
                    LastName = (string) col["LN"],
                    Email = (string) col["EM"],
                    UserId = (string) col["UID"],
                    Password = (string) col["PD"],
                    Title = (string) col["Title"]
                });
            }
            return newList;
        }
        catch (Exception)
        {
            return null;
        }

    }