Creating a MenuItem with a Shortcut of Control+Plus

I'm using the legacy WinForms MenuItem control in an application, and would like to implement zoom in and zoom out menu items (with Control++ and Control+- keyboard shortcuts). MenuItem does have a Shortcut property, of type Shortcut, but that doesn't have a CtrlPlus option.

I decided to look at how Shortcut was implemented in the referencesource, and it looks like the way that each of those enum values is just a combination of several Keys enum values (such as CtrlA being just Keys.Control + Keys.A). So I tried creating a custom Shortcut value that should be equal to Control+Plus:

const Shortcut CONTROL_PLUS = (Shortcut)(Keys.Control | Keys.Oemplus);

zoomInMenuItem.Shortcut = CONTROL_PLUS;

However, this throws an InvalidEnumArgumentException when I try to assign the Shortcut property.

So I've decided to use reflection, and modify the (not public) MenuItemData's shortcut property and then call the (non-public) UpdateMenuItem method. This actually works (with a side effect of displaying as Control+Oemplus in the menu item):

const Shortcut CONTROL_PLUS = (Shortcut)(Keys.Control | Keys.Oemplus);

var dataField = typeof(MenuItem).GetField("data", BindingFlags.NonPublic | BindingFlags.Instance);
var updateMenuItemMethod = typeof(MenuItem).GetMethod("UpdateMenuItem", BindingFlags.NonPublic | BindingFlags.Instance);
var menuItemDataShortcutField = typeof(MenuItem).GetNestedType("MenuItemData", BindingFlags.NonPublic)
    .GetField("shortcut", BindingFlags.NonPublic | BindingFlags.Instance);

var zoomInData = dataField.GetValue(zoomInMenuItem);
menuItemDataShortcutField.SetValue(zoomInData, CONTROL_PLUS);
updateMenuItemMethod.Invoke(zoomInMenuItem, new object[] { true });

While that method works, it uses reflection, and I'm not sure if it's future-proof.

I'm using MenuItem and not the newer ToolStripMenuItem because I need to have the RadioCheck property (among other reasons); switching away from that is not an option.

Here's some full code that creates the above dialog, which shows what I'm trying to accomplish (the most relevant code is in the OnLoad method):

ZoomForm.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Reflection;

namespace ZoomMenuItemMCVE
{
    public partial class ZoomForm : Form
    {
        private double zoom = 1.0;
        public double Zoom {
            get { return zoom; }
            set {
                zoom = value;
                zoomTextBox.Text = "Zoom: " + zoom;
            }
        }

        public ZoomForm() {
            InitializeComponent();
        }

        protected override void OnLoad(EventArgs e) {
            const Shortcut CONTROL_PLUS = (Shortcut)((int)Keys.Control + (int)Keys.Oemplus);
            const Shortcut CONTROL_MINUS = (Shortcut)((int)Keys.Control + (int)Keys.OemMinus);

            base.OnLoad(e);

            //We set menu later as otherwise the designer goes insane (http://ift.tt/1cOu2le)
            this.Menu = mainMenu;

            var dataField = typeof(MenuItem).GetField("data", BindingFlags.NonPublic | BindingFlags.Instance);
            var updateMenuItemMethod = typeof(MenuItem).GetMethod("UpdateMenuItem", BindingFlags.NonPublic | BindingFlags.Instance);
            var menuItemDataShortcutField = typeof(MenuItem).GetNestedType("MenuItemData", BindingFlags.NonPublic)
                .GetField("shortcut", BindingFlags.NonPublic | BindingFlags.Instance);

            var zoomInData = dataField.GetValue(zoomInMenuItem);
            menuItemDataShortcutField.SetValue(zoomInData, CONTROL_PLUS);
            updateMenuItemMethod.Invoke(zoomInMenuItem, new object[] { true });

            var zoomOutData = dataField.GetValue(zoomOutMenuItem);
            menuItemDataShortcutField.SetValue(zoomOutData, CONTROL_MINUS);
            updateMenuItemMethod.Invoke(zoomOutMenuItem, new object[] { true });
        }

        private void zoomInMenuItem_Click(object sender, EventArgs e) {
            Zoom *= 2;
        }

        private void zoomOutMenuItem_Click(object sender, EventArgs e) {
            Zoom /= 2;
        }
    }
}

ZoomForm.Designer.cs

namespace ZoomMenuItemMCVE
{
    partial class ZoomForm
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing) {
            if (disposing && (components != null)) {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent() {
            this.components = new System.ComponentModel.Container();
            System.Windows.Forms.MenuItem viewMenuItem;
            this.zoomTextBox = new System.Windows.Forms.TextBox();
            this.mainMenu = new System.Windows.Forms.MainMenu(this.components);
            this.zoomInMenuItem = new System.Windows.Forms.MenuItem();
            this.zoomOutMenuItem = new System.Windows.Forms.MenuItem();
            viewMenuItem = new System.Windows.Forms.MenuItem();
            this.SuspendLayout();
            // 
            // zoomTextBox
            // 
            this.zoomTextBox.Dock = System.Windows.Forms.DockStyle.Bottom;
            this.zoomTextBox.Location = new System.Drawing.Point(0, 81);
            this.zoomTextBox.Name = "zoomTextBox";
            this.zoomTextBox.ReadOnly = true;
            this.zoomTextBox.Size = new System.Drawing.Size(292, 20);
            this.zoomTextBox.TabIndex = 0;
            this.zoomTextBox.Text = "Zoom: 1.0";
            // 
            // mainMenu
            // 
            this.mainMenu.MenuItems.AddRange(new System.Windows.Forms.MenuItem[] {
            viewMenuItem});
            // 
            // viewMenuItem
            // 
            viewMenuItem.Index = 0;
            viewMenuItem.MenuItems.AddRange(new System.Windows.Forms.MenuItem[] {
            this.zoomInMenuItem,
            this.zoomOutMenuItem});
            viewMenuItem.Text = "View";
            // 
            // zoomInMenuItem
            // 
            this.zoomInMenuItem.Index = 0;
            this.zoomInMenuItem.Text = "Zoom in";
            this.zoomInMenuItem.Click += new System.EventHandler(this.zoomInMenuItem_Click);
            // 
            // zoomOutMenuItem
            // 
            this.zoomOutMenuItem.Index = 1;
            this.zoomOutMenuItem.Text = "Zoom out";
            this.zoomOutMenuItem.Click += new System.EventHandler(this.zoomOutMenuItem_Click);
            // 
            // ZoomForm
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(292, 101);
            this.Controls.Add(this.zoomTextBox);
            this.Name = "ZoomForm";
            this.Text = "ZoomForm";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.MainMenu mainMenu;
        private System.Windows.Forms.TextBox zoomTextBox;
        private System.Windows.Forms.MenuItem zoomInMenuItem;
        private System.Windows.Forms.MenuItem zoomOutMenuItem;
    }
}

The above code works and does what I want, but I'm not sure if it is the right way to do it (using reflection to modify a private variable generally seems like the incorrect method). My questions are:

• Is there a better way to set a MenuItem's shortcut to Control++?
• Is this reflection-based method going to cause issues?