public Task<bool> ExecuteAsync()

// Some times when using EditOperation.Modify you can unknowingly be attempting to set
//  an attribute to value 
//  setting 
// In this scenario the Modify action will detect that nothing is required
// and do nothing. Because no actions have occurred, the
// Consequently the Execute operation will fail. 
if (!opEdit.IsEmpty)
  opEdit.Execute();

var createFeatures = new EditOperation();
createFeatures.Name = "Create Features";
//Create a feature with a polygon
var token = createFeatures.Create(featureLayer, polygon);
if (createFeatures.IsSucceeded)
{
  // token.ObjectID wll be populated with the objectID of the created feature after Execute has been successful
}
//Do a create features and set attributes
var attributes = new Dictionary<string, object>();
attributes.Add("SHAPE", polygon);
attributes.Add("NAME", "Corner Market");
attributes.Add("SIZE", 1200.5);
attributes.Add("DESCRIPTION", "Corner Market");

createFeatures.Create(featureLayer, attributes);

//Create features using the current template
//Must be within a MapTool
createFeatures.Create(this.CurrentTemplate, polygon);

//Execute to execute the operation
//Must be called within QueuedTask.Run

if (!createFeatures.IsEmpty)
{
  createFeatures.Execute(); //Execute will return true if the operation was successful and false if not.
}

//or use async flavor
//await createFeatures.ExecuteAsync();