//属于命令ChatWithUserCommand private void ChatWithUser(object obj) { ChatListVisibility = Visibility.Visible; ChatMainVisibility = Visibility.Visible; FriendListVisibility = Visibility.Hidden; FriendMainVisibility = Visibility.Hidden; //查看有无现有聊天 bool ExistChat = false; if (Chats.Count != 0) { var searchedChats = from c in Chats where c.Name == selectedUser.NickName select c; if (searchedChats.Count() != 0) { ExistChat = true; } } //若已存在,则进入聊天 if (ExistChat) { SelectedChat = (from c in Chats where c.Name == selectedUser.NickName select c).Single(); } //若不存在,则创建聊天 else { PrivateChat newPrivateChat = new PrivateChat(selectedUser); Chats.Add(newPrivateChat); SelectedChat = newPrivateChat; dataService.GetAllChats(); Utilities.Messenger.Default.Send(new UpdateChatsMessage(Chats)); } }