Avoid duplicate accelerators

TypeName	AvoidDuplicateAccelerators
CheckId	CA1301
Category	Microsoft.Globalization
Breaking Change	NonBreaking

Cause

A type extends System.Windows.Forms.Control and contains two or more top level controls with identical access keys that are stored in a resource file.

Rule Description

An access key, also known as an accelerator, allows keyboard access to a control using the ALT key. When multiple controls have duplicate access keys, the behavior of the access key is not well defined. The user might not be able to access the intended control using the access key and a control other than the one intended might be activated.

The current implementation of this rule ignores menu items. However, menu items in the same submenu should not have identical access keys.

How to Fix Violations

To fix a violation of this rule, define unique access keys for all controls.

When to Exclude Warnings

Do not exclude a warning from this rule.

Example

The following example shows a minimal form that contains two controls with identical access keys. The keys are stored in a resource file, which is not shown; however, their values appear in the commented out checkBox.Text lines. The behavior of duplicate accelerators can be examined by exchanging the checkBox.Text lines with their commented out counterparts. However, in this case, the example will not generate a warning from the rule.

using System;
using System.Drawing;
using System.Resources;
using System.Windows.Forms;

namespace GlobalizationLibrary
{
   public class DuplicateAccelerators : Form
   {
      [STAThread]
      public static void Main()
      {
         DuplicateAccelerators accelerators = new DuplicateAccelerators();
         Application.Run(accelerators);
      }

      private CheckBox checkBox1;
      private CheckBox checkBox2;

      public DuplicateAccelerators()
      {
         ResourceManager resources = 
            new ResourceManager(typeof(DuplicateAccelerators));

         checkBox1 = new CheckBox();
         checkBox1.Location = new Point(8, 16);
         // checkBox1.Text = "&checkBox1";
         checkBox1.Text = resources.GetString("checkBox1.Text");

         checkBox2 = new CheckBox();
         checkBox2.Location = new Point(8, 56);
         // checkBox2.Text = "&checkBox2";
         checkBox2.Text = resources.GetString("checkBox2.Text");

         Controls.Add(checkBox1);
         Controls.Add(checkBox2);
      }
   }
}

See Also

Reference

System.Resources.ResourceManager

Concepts

Resources in Applications