面板中的面板，自动滚动

在使用WinForms的真实程序遇到问题后，我正在做一个极简主义测试应用程序。我把一个小面板（子面板）放在一个大面板（父面板）里。较大的面板将AutoScroll设置为true。子面板的默认"锚点"设置为"顶部"answers"左侧"。子面板未停靠。

我想要的行为是，每当较小面板的位置偏移过大时，滚动条就会出现，无论是顶部、底部、左侧还是右侧。问题是，只有当它太右，或者在底部太远时，它才会起作用。当滚动条在顶部过多或在左侧过多时，不会出现滚动条。

我使用两个简单的按钮来强制子面板的位置向左200像素，或向右200像素，以便快速修改其位置。

这是我的Form1（）代码：

        private void button1_Click(object sender, EventArgs e)
    {
        childPanel.Location = new Point(childPanel.Location.X - 200, childPanel.Location.Y);
        hostPanel.Invalidate();
    }
    private void button2_Click(object sender, EventArgs e)
    {
        childPanel.Location = new Point(childPanel.Location.X + 200, childPanel.Location.Y);
        hostPanel.Invalidate();
    }

这是设计师代码：

       private void InitializeComponent()
    {
        this.hostPanel = new System.Windows.Forms.Panel();
        this.childPanel = new System.Windows.Forms.Panel();
        this.moveChildLeft = new System.Windows.Forms.Button();
        this.moveChildRight = new System.Windows.Forms.Button();
        this.hostPanel.SuspendLayout();
        this.SuspendLayout();
        // 
        // hostPanel
        // 
        this.hostPanel.AutoScroll = true;
        this.hostPanel.BackColor = System.Drawing.SystemColors.AppWorkspace;
        this.hostPanel.Controls.Add(this.childPanel);
        this.hostPanel.Location = new System.Drawing.Point(239, 48);
        this.hostPanel.Name = "hostPanel";
        this.hostPanel.Size = new System.Drawing.Size(400, 400);
        this.hostPanel.TabIndex = 0;
        // 
        // childPanel
        // 
        this.childPanel.BackColor = System.Drawing.SystemColors.ButtonHighlight;
        this.childPanel.Location = new System.Drawing.Point(29, 62);
        this.childPanel.Name = "childPanel";
        this.childPanel.Size = new System.Drawing.Size(342, 259);
        this.childPanel.TabIndex = 0;
        // 
        // moveChildLeft
        // 
        this.moveChildLeft.Location = new System.Drawing.Point(61, 81);
        this.moveChildLeft.Name = "moveChildLeft";
        this.moveChildLeft.Size = new System.Drawing.Size(75, 23);
        this.moveChildLeft.TabIndex = 1;
        this.moveChildLeft.Text = "Left 200";
        this.moveChildLeft.UseVisualStyleBackColor = true;
        this.moveChildLeft.Click += new System.EventHandler(this.button1_Click);
        // 
        // moveChildRight
        // 
        this.moveChildRight.Location = new System.Drawing.Point(61, 111);
        this.moveChildRight.Name = "moveChildRight";
        this.moveChildRight.Size = new System.Drawing.Size(75, 23);
        this.moveChildRight.TabIndex = 2;
        this.moveChildRight.Text = "Right 200";
        this.moveChildRight.UseVisualStyleBackColor = true;
        this.moveChildRight.Click += new System.EventHandler(this.button2_Click);
        // 
        // Form1
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(1018, 549);
        this.Controls.Add(this.moveChildRight);
        this.Controls.Add(this.moveChildLeft);
        this.Controls.Add(this.hostPanel);
        this.Name = "Form1";
        this.Text = "Form1";
        this.hostPanel.ResumeLayout(false);
        this.ResumeLayout(false);
    }

<Window x:Class="WpfApplication4.Window3"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window3" WindowState="Maximized">
    <DockPanel>
        <StackPanel DockPanel.Dock="Top" Orientation="Horizontal">
            <Button Content="Left" Click="MoveLeft"/>
            <Button Content="Right" Click="MoveRight"/>
        </StackPanel>
        <Border BorderBrush="Blue" BorderThickness="1" Width="300" Height="300">
            <ScrollViewer VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" x:Name="Scr">
                <Grid Background="Green" Width="100" Height="100" x:Name="Grid"/>
            </ScrollViewer>
        </Border>
    </DockPanel>
</Window>

using System.Windows;
namespace WpfApplication4
{
    public partial class Window3 : Window
    {
        public Window3()
        {
            InitializeComponent();
        }
        private void MoveRight(object sender, RoutedEventArgs e)
        {
            if (Grid.Margin.Right <= 0)
            {
                Grid.Margin = new Thickness(Grid.Margin.Left + 100,0,0,0);
            }
            else
            {
                Grid.Margin = new Thickness(0, 0, Grid.Margin.Right - 100, 0);
                Scr.ScrollToHorizontalOffset(Scr.HorizontalOffset - 100);
            }
        }
        private void MoveLeft(object sender, RoutedEventArgs e)
        {
            if (Grid.Margin.Left > 0)
            {
                Grid.Margin = new Thickness(Grid.Margin.Left - 100, 0, 0, 0);
            }
            else
            {
                Grid.Margin = new Thickness(0, 0, Grid.Margin.Right + 100, 0);
                Scr.ScrollToHorizontalOffset(Scr.HorizontalOffset + 100);
            }
        }
    }
}