silverlight中连接数据库无法更新

各位大声能否帮我解决一下 为什么 我在datagrid中更新数据 却无法更新到数据库中吗 我已经用了submitchanges（）函数啦，是否还有什么关键语句吗？代码如下public partial class MainPage : UserControl
    {
        private CustomerDomainContext _customerContext = new CustomerDomainContext();        public MainPage()
        {
            InitializeComponent();           LoadOperation<Customer> loadOp = this._customerContext.Load(this._customerContext.GetCustomerQuery ());
           CustomerGrid.ItemsSource = loadOp.Entities;
        }        private void LetterButton_Click(object sender, RoutedEventArgs e)
        {
            IDButton.IsEnabled = false;
            LetterButton.IsEnabled = false;
            LoadOperation<Customer> loadOp = this._customerContext.Load(this._customerContext.GetCustomersByLastNameLetterQuery(LetterValue.Text), CustomerLoadedCallback, null);
            CustomerGrid.ItemsSource = loadOp.Entities;
        }        private void IDButton_Click(object sender, RoutedEventArgs e)
        {
            IDButton.IsEnabled = false;
            LetterButton.IsEnabled = false;
            LoadOperation<Customer> loadOp =     this._customerContext.Load(this._customerContext.GetCustomersByIDQuery(int.Parse(IDValue.Text)), CustomerLoadedCallback, null);
            CustomerGrid.ItemsSource = loadOp.Entities;
        }        void CustomerLoadedCallback(LoadOperation<Customer> loadOperation)
        {
            IDButton.IsEnabled = true;
            LetterButton.IsEnabled = true;
        }        private void SaveButton_Click(object sender, RoutedEventArgs e)
        {
            _customerContext.SubmitChanges(OnSubmitCompleted, null);
        }        private void RejectButton_Click(object sender, RoutedEventArgs e)
        {
            _customerContext.RejectChanges();
            CheckChanges();
        }        private void CustomerGrid_RowEditEnded(object sender, DataGridRowEditEndedEventArgs e)
        {
            
            CustomerGrid.CommitEdit(DataGridEditingUnit.Row, true);
            
            //_customerContext.SubmitChanges();
            CheckChanges();
        }        private void CheckChanges()
        {
            EntityChangeSet changeSet = _customerContext.EntityContainer.GetChanges();
            ChangeText.Text = changeSet.ToString();            bool hasChanges = _customerContext.HasChanges;
            SaveButton.IsEnabled = hasChanges;
            RejectButton.IsEnabled = hasChanges;
        }        private void OnSubmitCompleted(SubmitOperation so)
        {
            if (so.HasError)
            {
                MessageBox.Show(string.Format("Submit Failed: {0}", so.Error.Message));
                so.MarkErrorAsHandled();
            }
            CheckChanges();
        }              
    }