Switch Statement: A constant value is expected

[HaLo2FrEeEk]

I'm trying to make a switch statement that will handle hotkeys assigned to different functions in my application. The hotkeys will be user-changable, so I've got them saved as application settings. I have a class that allows the program to hook the keyboard and accept the hotkeys even if the program doesn't have focus. In the event handler for that hook I'm trying to create a switch statement that looks like this:

switch (e.KeyCode)
            {
                case settings.hotkey1:
                    MessageBox.Show("Hot Key 1");
                    break;
                case settings.hotkey2:
                    MessageBox.Show("Hot Key 2");
                    break;
            }

But I'm getting an error:

"A constant value is expected"

I don't know what that means though. All I want is for the first case to fire if e.KeyCode equals the one I have saved for hotkey1, and the same for if e.KeyCode is hotkey2. How can I make it let me do that? I don't want to have a bunch of if statements, that would defeat the purpose of a switch statement existing.

Any ideas?

[Alex Papadimoulis]

You cannot accomplish this with a switch statement, and you will instead have to use an if/else construct.

if (e.KeyCode == settings.hotkey1)
  MessageBox.Show("Hot Key 1");
else if (e.KeyCode == settings.hotkey2)
  MessageBox.Show("Hot Key 2");

It's "just the way it is," as the switch statement requires that only integers (enums) and strings be used.


##
As an aside, if anyone has any opinions/ideas as to why, I'd love to hear them. I do understand that there is an MSIL instruction called Switch, and that it jumps based off of a jump table... but the compiler of course can't use Switch if strings are used as cases. When that happens, it seems to generate an if/else block. Why can't the compiler do that for complex types?

[HaLo2FrEeEk]

So an Enum would work. Well...at runtime could I generate an enum with my settings values? There are only 2 hotkeys now, but I'd like to add more later. Is it possible to dynamically construct an Enum?

[GaryTexmo]

You can set up a hash table where the key pressed maps to an action, which is set up in an enum. Then you can switch on the action and do whatever...

enum Action
{
  NoAction,
  Save,
  Load,
  Open
}

Hashtable keybinds = new HashTable();

keybinds.Add(Keys.S, Action.Save);
keybinds.Add(Keys.O, Action.Save);
// .. and so on

switch (keybinds[pressedKey])
{
  case Action.Save:
    // do stuff
    break;
  // and so on
}

[HaLo2FrEeEk]

But can I generate that Enum based on the data I have saved in the settings file? I'd like my users to be able to change the default hotkeys, which is why I'm using a settings file.

[GaryTexmo]

You don't generate the enum based on the data... the enum represents which action you take. You generate the hash mapping from a key to an action based on the data.

Unless there's something more I'm not getting... do you know what the actions are beforehand? You just don't know what key does what, right?

[HaLo2FrEeEk]

Correct. I want the user to be able to set the hotkey to whatever they want, so I suppose you're right about generating the hashtable. Thanks.