Windows 窗体 - Tab 键在子面板中不起作用

我有一个包含一些文本框和按钮的表单子面板.我尝试为这些控件设置 tabstop 和 tabindex 属性，以便用户可以从一个控件切换到下一个控件.但是由于某种原因，tabbing 不起作用，curor 停留在我按下 tab 键时具有焦点的同一个字段上.我在 .Net 3.5 框架中使用 C#.下面是我的代码的样子 -

I have a child panel in a form which contains some text boxes and buttons. I tried setting tabstop and tabindex properties for these controls so that the user can tab from one control to the next. But for some reason the tabbing does not work, the curor stays on the same field which has the focus when I press the tab key. I am using C# with .Net 3.5 framework. Below is how my code looks like -

  rightPanel.Controls.Clear();
        marketMessageLabel = new Label();
        marketMessageLabel.Location = new Point(0, 20);            
        marketMessageLabel.AutoSize = false;
        marketMessageLabel.Size = new Size(rightPanel.Width, 42);
        marketMessageLabel.BackColor = Color.White;            
        marketMessageLabel.Font = new System.Drawing.Font("Verdana", 8.00F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
        rightPanel.Controls.Add(marketMessageLabel);                        

        signinUserNameLabel = new Label();
        signinUserNameLabel.Location = new Point(0, 150);
        signinUserNameLabel.Size = new Size(60, 14);
        signinUserNameLabel.BackColor = Color.White;
        signinUserNameLabel.Text = "User Name";            
        signinUserNameLabel.Font = new System.Drawing.Font("Verdana", 9.00F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
        rightPanel.Controls.Add(signinUserNameLabel);

        signinUserNameTextBox = new TextBox();
        signinUserNameTextBox.Location = new Point(0, 170);
        signinUserNameTextBox.Width = this.Width - 80;
        signinUserNameTextBox.Font = new System.Drawing.Font("Verdana", 9.00F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));         
        signinUserNameTextBox.TabIndex = 0;
        signinUserNameTextBox.TabStop = true;

        rightPanel.Controls.Add(signinUserNameTextBox);

        signinPasswordLabel = new Label();
        signinPasswordLabel.Location = new Point(0, 192);
        signinPasswordLabel.Size = new Size(100, 14);
        signinPasswordLabel.Font = new System.Drawing.Font("Verdana", 9.00F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
        signinPasswordLabel.BackColor = Color.White;
        signinPasswordLabel.Text = "Password";            
        rightPanel.Controls.Add(signinPasswordLabel);                      

        signinPasswordTextBox = new TextBox();
        signinPasswordTextBox.Location = new Point(0, 210);
        signinPasswordTextBox.Width = this.Width - 80;            
        signinPasswordTextBox.PasswordChar = '*';
        signinPasswordTextBox.TabIndex = 1;
        signinPasswordTextBox.TabStop = true;
        rightPanel.Controls.Add(signinPasswordTextBox);

        signInButton = new Button();
        signInButton.Text = "Sign In";
        signInButton.Font = new System.Drawing.Font("Verdana", 9.00F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
        signInButton.Width = 70;            
        signInButton.BackColor = Color.White;
        signInButton.Location = new Point(0,240);
        signInButton.Click += new EventHandler(signInButton_Click);
        signInButton.TabIndex = 2;
        signInButton.TabStop = true;
        rightPanel.Controls.Add(signInButton);