Event Sourcing & CQRS Pattern for SPA

service-change-username.cs

public async Task<UsernameChangeResponse> ChangeUsernameAsync(UsernameChangeRequest request)
{
  var handler = this._handlers.SingleOrDefault(p => p.CanHandle(request));

  var ev = handler.CreateEvent(request) as UsernameChangedEvent;

  await this._processor.ProcessEventsAsync(new[] { ev });
  var response = new UsernameChangeResponse()
                     {
                       Data = new UsernameResponseData()
                                  {
                                    Value = request.Value
                                  }
                     };

  return await Task.FromResult(response);
}