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FeatureLayer fl = MyMap.Layers["MyFeatureLayer"] as FeatureLayer;
fl.UpdateCompleted += MyFeatureLayer_UpdateCompleted;
fl.UpdateFailed += new EventHandler<TaskFailedEventArgs>(MyFeatureLayer_UpdateFailed);
private void MyFeatureLayer_UpdateFailed(object sender, EventArgs args)
{
FeatureLayer fl = sender as FeatureLayer;
// display any errors if any (optional).
}