如何使分组框的大小和布局的内容一致

<GroupBox Header="My GroupBox">
    <StackPanel>
        <Button Content="Button 1" />
        <Button Content="Button 2" />
        <TextBox Text="Some text" />
    </StackPanel>
</GroupBox>

GroupBox groupBox = new GroupBox();
groupBox.Text = "My GroupBox";
groupBox.AutoSize = true;
groupBox.AutoSizeMode = AutoSizeMode.GrowAndShrink;

Button button1 = new Button();
button1.Text = "Button 1";
Button button2 = new Button();
button2.Text = "Button 2";
TextBox textBox = new TextBox();
textBox.Text = "Some text";

groupBox.Controls.Add(button1);
groupBox.Controls.Add(button2);
groupBox.Controls.Add(textBox);

this.Controls.Add(groupBox);

<GroupBox Header="My GroupBox">
    <ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
        <StackPanel>
            <Button Content="Button 1" />
            <Button Content="Button 2" />
            <TextBox Text="Some text" Height="100" />
            <!-- 更多控件 -->
        </StackPanel>
    </ScrollViewer>
</GroupBox>