void Create() { if (LessonRepository.Lessons.Where(l => l.Name == LessonName).Count() > 0) { NotifierVm nvm = new NotifierVm() { Message = "Lesson name already exists. Please choose another one.", Buttons = NotifierButtons.Ok, Title = "Invalid Entry!" }; DialogService.ShowDialog(nvm); return; } if (string.IsNullOrEmpty(LessonName)) { DialogService.ShowDialog(new NotifierVm("Lesson Name cannot be empty!.", "Invalid Entry!")); return; } if (string.IsNullOrEmpty(LessonText)) { DialogService.ShowDialog(new NotifierVm("Lesson text cannot be empyt!.", "Invalid Entry")); return; } LessonRepository.AddLesson(new UserLesson() { Name = LessonName, Text = new string(LessonText.Replace("\r", "").Replace("\n", "").Take(300).ToArray()), OwnerId = StudentRepository.Logged.Id }); DialogService.ShowDialog(new NotifierVm("Lesson created successfully!.", "Success")); Close(); }