Convertion problem in with WCF service for silverlight app

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C#

ASP.NET

WCF

Silverlight

C#4.0

Hi,
I have a silverlight app in which i consume WCF service for showing record from database.
data is passed from WCF to Silvelight in List<> having store in class variable.
but when i am binding the result with datagrid of silverlight then an error:-

Error 1 Cannot implicitly convert type 'AdWorldSilverLightApp.ServiceReference1.fetchUserRecordResponseFetchUserRecordResult' to 'System.Collections.IEnumerable'. An explicit conversion exists (are you missing a cast?) F:\balwant\TestApp\AdWorldSilverLightApp\AdWorldSilverLightApp\ShowUser.xaml.cs 43 36 AdWorldSilverLightApp

occurs.
silverlight xaml.cs code is as:-

public ShowUser()
       {
           InitializeComponent();
           ServiceReference1.MyServiceClient newclient = new ServiceReference1.MyServiceClient();
           newclient.fetchUserRecordCompleted += new EventHandler<ServiceReference1.fetchUserRecordCompletedEventArgs>(newclient_fetchUserRecordCompleted);
           newclient.fetchUserRecordAsync();
       }
       void newclient_fetchUserRecordCompleted(object sender, ServiceReference1.fetchUserRecordCompletedEventArgs e)
       {

           ShowGrid.ItemsSource = e.Result;
       }

and WCF service code is as:-

public class UserMaster
       {
           public string UserName { get; set; }
           public string Password { get; set; }
           public string FirstName { get; set; }
           public string LastName { get; set; }
           public string Email { get; set; }
           public string Address { get; set; }
           public string MatrialStatus { get; set; }
           public string Moblie { get; set; }
       }
 public List<UserMaster> fetchUserRecord()
        {
            var Record = new List<UserMaster>();
            SqlConnection con = new SqlConnection();
            con.ConnectionString = WebConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            con.Open();
            cmd.CommandText = "select * from UserMaster";
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            da.Fill(dt);
            if (dt.Rows.Count > 0)
            {
                for (int i = 0; i <= dt.Rows.Count; i++)
                {
                    var user = new UserMaster
                    {
                        UserName = dt.Rows[i]["UserName"].ToString(),
                        Password=dt.Rows[i]["Password"].ToString(),
                        FirstName = dt.Rows[i]["FirstName"].ToString(),
                        LastName = dt.Rows[i]["LastName"].ToString(),
                        Email = dt.Rows[i]["Email"].ToString(),
                        Address = dt.Rows[i]["Address"].ToString(),
                        MatrialStatus = dt.Rows[i]["MatrialStatus"].ToString(),
                        Moblie = dt.Rows[i]["Moblie"].ToString()
                    };
                    Record.Add(user);


                }
                
            }
          
            return Record;
            // return dt;
        }

Please help me.
thanks