在用户控件内部显示控件，而不是其父控件的边界 [英] Show control inside user control outside the boundaries of its parent

问题描述

我有一个用户控件，该控件具有一个文本框和一个列表框，它使用它们来为用户提供自动完成功能.

I have a usercontrol that has a textbox and a listbox, and it uses them to provides autocomplete functionality to the users.

但是，我希望将列表框绘制在用户控件的边界之外，这样当必须在用户控件的边缘附近绘制列表框时，它不会被截断.有关如何操作的任何提示?本质上，我希望一个列表框浮动在其容器控件的边界之外.

However, I want the listbox to be drawn outside of the boundaries of the user control so that it doesn't get cutoff when the listbox has to be drawn near the edge of the user control. Any tips on how to do that? Essentially I want a listbox floating outside the boundaries of its container control.

我唯一可以考虑的方法是在实例化时将对外部列表框的引用传递给用户控件，然后操纵该列表框，而不是将其包含在用户控件中，但是我不喜欢这种方法.提前致谢.

The only way I can think off is to pass a reference to an outside listbox to the user control on instantiation and then manipulate that listbox instead of having it inside the user control, but I dont like this approach. Thanks in advance.

推荐答案

问题是，您无法摆脱容器形式的界限，但可以将控件托管在其他地方.

Problem is, you can't escape your container form bounds, but you can host your control somewhere else.

这是我通过滥用ToolstripDropDown类(我使用它在大型企业应用程序中显示日期选择器)来进行的工作:

Here's what I got working by abusing the ToolstripDropDown class (I use it to display datepickers in a large enterprise application):

/// <summary>
/// PopupHelper
/// </summary>
public sealed class PopupHelper : IDisposable
{
    private readonly Control m_control;
    private readonly ToolStripDropDown m_tsdd;
    private readonly Panel m_hostPanel; // workarround - some controls don't display correctly if they are hosted directly in ToolStripControlHost

    public PopupHelper(Control pControl)
    {
        m_hostPanel = new Panel();
        m_hostPanel.Padding = Padding.Empty;
        m_hostPanel.Margin = Padding.Empty;
        m_hostPanel.TabStop = false;
        m_hostPanel.BorderStyle = BorderStyle.None;
        m_hostPanel.BackColor = Color.Transparent;

        m_tsdd = new ToolStripDropDown();
        m_tsdd.CausesValidation = false;

        m_tsdd.Padding = Padding.Empty;
        m_tsdd.Margin = Padding.Empty;
        m_tsdd.Opacity = 0.9;

        m_control = pControl;
        m_control.CausesValidation = false;
        m_control.Resize += MControlResize;

        m_hostPanel.Controls.Add(m_control);

        m_tsdd.Padding = Padding.Empty;
        m_tsdd.Margin = Padding.Empty;

        m_tsdd.MinimumSize = m_tsdd.MaximumSize = m_tsdd.Size = pControl.Size;

        m_tsdd.Items.Add(new ToolStripControlHost(m_hostPanel));
    }

    private void ResizeWindow()
    {
        m_tsdd.MinimumSize = m_tsdd.MaximumSize = m_tsdd.Size = m_control.Size;
        m_hostPanel.MinimumSize = m_hostPanel.MaximumSize = m_hostPanel.Size = m_control.Size;
    }

    private void MControlResize(object sender, EventArgs e)
    {
        ResizeWindow();
    }

    /// <summary>
    /// Display the popup and keep the focus
    /// </summary>
    /// <param name="pParentControl"></param>
    public void Show(Control pParentControl)
    {
        if (pParentControl == null) return;

        // position the popup window
        var loc = pParentControl.PointToScreen(new Point(0, pParentControl.Height));
        m_tsdd.Show(loc);
        m_control.Focus();
    }

    public void Close()
    {
        m_tsdd.Close();
    }

    public void Dispose()
    {
        m_control.Resize -= MControlResize;

        m_tsdd.Dispose();
        m_hostPanel.Dispose();
    }
}

用法:

    private PopupHelper m_popup;
    private void ShowPopup()
    {
        if (m_popup == null)
            m_popup = new PopupHelper(yourListControl);

        m_popup.Show(this);
    }

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