C＃我不明白爲什麼這個按鈕不會刪除

Question

基本上......當用戶接受或拒絕好友請求時，它應該刪除用戶的名稱，接受和拒絕按鈕，但它只會刪除用戶的名稱和拒絕按鈕。我不明白。代碼：

 private void loadFriendRequests() 
    { 
     using (SqlConnection connection = new SqlConnection(con)) 
     { 
      using (SqlCommand cmd = new SqlCommand(@"Select IDRequest, UserFirstName, UserLastName, FriendEmail From PendingRequests Where FriendEmail = @fe", connection)) 
      { 
       connection.Open(); 
       cmd.Parameters.AddWithValue("@fe", Properties.Settings.Default.Email); 
       using (SqlDataReader dr = cmd.ExecuteReader()) 
       { 
        int i = 0; 
        while (dr.Read()) 
        { 
         i++; 
         foreach (object request in i.ToString()) 
         { 
          Label userName = new Label(); 
          Button accept = new Button(); 
          Button reject = new Button(); 
          accept.Text = "Accept"; 
          reject.Text = "Reject"; 
          int idRequest = Convert.ToInt32(dr["IDRequest"]); 
          userName.Text = CultureInfo.CurrentCulture.TextInfo.ToTitleCase(dr["UserFirstName"].ToString() + " " + dr["UserLastName"].ToString()); 
          userName.Tag = idRequest; 
          accept.Tag = idRequest; 
          reject.Tag = idRequest; 

          accept.Click += Accept_Click; 
          reject.Click += Reject_Click; 

          friendRequestPanel.Controls.Add(userName); 
          friendRequestPanel.Controls.Add(accept); 
          friendRequestPanel.Controls.Add(reject); 
         } 
        } 
       } 
      } 
     } 
     Requests.Start(); 
    } 
    private void Reject_Click(object sender, EventArgs e) 
    { 
     Button c = sender as Button; 
     int idRequest = Convert.ToInt32(c.Tag); 
     var ctrls = friendRequestPanel.Controls 
             .Cast<Control>() 
             .Where(x => 
              Convert.ToInt32(x.Tag) == idRequest); 
     foreach (Control ct in ctrls) 
     { 
      friendRequestPanel.Controls.Remove(ct); 
      ct.Dispose(); 
     } 
     updateFriendRequestDatabase(2); 
    } 
    private void Accept_Click(object sender, EventArgs e) 
    { 
     Button c = sender as Button; 
     int idRequest = Convert.ToInt32(c.Tag); 
     var ctrls = friendRequestPanel.Controls 
             .Cast<Control>() 
             .Where(x => x.Tag != null && 
              Convert.ToInt32(x.Tag) == idRequest); 
     foreach (Control ct in ctrls) 
     { 
      friendRequestPanel.Controls.Remove(ct); 
      ct.Dispose(); 
     } 
     updateFriendRequestDatabase(1); 

    } 

圖片：GUI

當任一按鈕被點擊：GUI

爲什麼沒有刪除 '接受' 按鈕？

Answer 1

您在循環中更改集合。爲了解決這個問題，你可以在你找到的控制條件結尾調用ToList，並循環結果。這樣一來，你是通過不同的列表比收集循環要更改：

var ctrls = friendRequestPanel.Controls.Cast<Control>() 
           .Where(Convert.ToInt32(x.Tag) == idRequest) 
           .ToList(); //<--- Creates a new List<Control> 
foreach (Control ct in ctrls) 
{ 
    friendRequestPanel.Controls.Remove(ct); 
    ct.Dispose(); 
}