Extension methods for classes in the System.Windows.Forms namespace.

WinFormExtensions.cs

// Copyright Matthew King 2012-2015.
// Distributed under the Boost Software License, Version 1.0.
// (See http://www.boost.org/LICENSE_1_0.txt)

using System;
using System.Drawing;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

/// <summary>
/// Extension methods for classes in the System.Windows.Forms namespace.
/// </summary>
public static class WinFormExtensions
{
    /// <summary>
    /// Checks if this System.Windows.Forms.TreeNode is a descendant of the specified
    /// System.Windows.Forms.TreeNode.
    /// </summary>
    /// <param name="node">
    /// A System.Windows.Forms.TreeNode instance.
    /// </param>
    /// <param name="ancestor">
    /// The System.Windows.Forms.TreeNode instance that is a potential ancestor of this
    /// System.Windows.Forms.TreeNode instance.
    /// </param>
    /// <returns>
    /// true if this System.Windows.Forms.TreeNode is a descendant of the specified
    /// System.Windows.Forms.TreeNode; otherwise, false.
    /// </returns>
    public static bool IsDescendantOf(this TreeNode node, TreeNode ancestor)
    {
        if (node == null)
            throw new ArgumentNullException("node", "node should not be null.");

        if (ancestor == null)
            throw new ArgumentNullException("ancestor", "ancestor should not be null.");

        if (node.Parent == null)
            return false;

        if (node.Parent == ancestor)
            return true;

        return WinFormExtensions.IsDescendantOf(node.Parent, ancestor);
    }

    /// <summary>
    /// Checks if this System.Windows.Forms.TreeNode is an ancestor of the specified
    /// System.Windows.Forms.TreeNode.
    /// </summary>
    /// <param name="node">
    /// A System.Windows.Forms.TreeNode instance.
    /// </param>
    /// <param name="descendant">
    /// The System.Windows.Forms.TreeNode instance that is a potential descendant of this
    /// System.Windows.Forms.TreeNode instance.
    /// </param>
    /// <returns>
    /// true if this System.Windows.Forms.TreeNode is an ancestor of the specified
    /// System.Windows.Forms.TreeNode; otherwise, false.
    /// </returns>
    public static bool IsAncestorOf(this TreeNode node, TreeNode descendant)
    {
        if (node == null)
            throw new ArgumentNullException("node", "node should not be null.");

        if (descendant == null)
            throw new ArgumentNullException("descendant", "descendant should not be null.");

        if (node.Nodes.Count == 0)
            return false;

        if (node.Nodes.Contains(descendant))
            return true;

        return node.Nodes
            .OfType<TreeNode>()
            .Any(n => WinFormExtensions.IsAncestorOf(n, descendant));
    }

    /// <summary>
    /// Shows the form to the user.
    /// </summary>
    /// <param name="form">
    /// The form to show.
    /// </param>
    /// <returns>
    /// A task representing the asynchronous operation.
    /// </returns>
    public static Task<DialogResult> ShowAsync(this Form form)
    {
        if (form == null)
            throw new ArgumentNullException("form", "form should not be null.");

        return ShowAsync(form, null);
    }

    /// <summary>
    /// Shows the form with the specified owner to the user.
    /// </summary>
    /// <param name="form">
    /// The form to show.
    /// </param>
    /// <param name="owner">
    /// Any object that implements System.Windows.Forms.IWin32Window and represents
    /// the top-level window that will own the form.
    /// </param>
    /// <returns>
    /// A task representing the asynchronous operation.
    /// </returns>
    public static Task<DialogResult> ShowAsync(this Form form, IWin32Window owner)
    {
        if (form == null)
            throw new ArgumentNullException("form", "form should not be null.");

        TaskCompletionSource<DialogResult> tcs = new TaskCompletionSource<DialogResult>();

        FormClosingEventHandler handler = null;
        handler = new FormClosingEventHandler((s, e) =>
        {
            form.FormClosing -= handler;
            tcs.SetResult(form.DialogResult);
        });

        form.FormClosing += handler;

        form.Show(owner);

        return tcs.Task;
    }

    /// <summary>
    /// Shows the System.Windows.Forms.ContextMenuStrip relative to the specified
    /// System.Windows.Forms.Control location.
    /// </summary>
    /// <param name="menu">
    /// The System.Windows.Forms.ContextMenuStrip to show.
    /// </param>
    /// <param name="control">
    /// The System.Windows.Forms.Control that is the reference point for the
    /// System.Windows.Forms.ContextMenuStrip position.
    /// </param>
    /// <param name="pos">
    /// The horizontal and vertical location of the reference control's upper-left corner,
    /// in pixels.
    /// </param>
    /// <returns>
    /// A task representing the asynchronous operation.
    /// </returns>
    public static Task ShowAsync(this ContextMenuStrip menu, Control control, Point pos)
    {
        if (menu == null)
            throw new ArgumentNullException("menu", "menu should not be null.");

        if (control == null)
            throw new ArgumentNullException("control", "control should not be null.");

        TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();

        ToolStripDropDownClosedEventHandler handler = null;
        handler = new ToolStripDropDownClosedEventHandler((s, e) =>
        {
            menu.Closed -= handler;
            tcs.SetResult(true);
        });

        menu.Closed += handler;

        menu.Show(control, pos);

        return tcs.Task;
    }
}