Windows 窗体 - Tab 键在子面板中不起作用

我有一个表单中的子面板，其中包含一些文本框和按钮。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。但由于某种原因，制表符不起作用，当我按 Tab 键时，光标停留在具有焦点的同一字段上。我正在使用 C# 和 .Net 3.5 框架。下面是我的代码的样子 -

  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);

另一个可能的问题是，如果“选项卡”不起作用的表单位于未模态显示的表单上。

由于某些原因，如果子表单显示为“制表符”，则有时无法使用.show，并且您宁愿用以下方式显示表单.ShowDialog.