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Why is an if statement working but not a switch statement

Title is terrible, but I wasn't too sure what to put.

I'm trying to create Switch Statement using the char index of a string and an Enum using this wrapper to get the value of the selected enum from a Description, it pretty much allows you to store a string to an enum value.

Here is my if statement

Switch Statement

if statement

if (msgComingFromFoo[1] == Convert.ToChar(Message.Code.FOO_TRIGGER_SIGNAL.EnumDescriptionToString()))
{
//foo
}


and here is my Switch statement

Switch statement

switch (msgComingFromFoo[1])
{
case Convert.ToChar(Message.Code.FOO_TRIGGER_SIGNAL.EnumDescriptionToString()):
break;
}


Why is it accepting the if statement and not the switch statement?

I tried converting it to a char since I'm selected an index from a string, but unfortunately i didn't work.

if statement

switch statement

Update:

Here is the Message.Code Enum

Message.Code

public class Message
{
public enum Code
{
[Description("A")]
FOO_TRIGGER_SIGNAL
}
}


As you can see, I need the Description assigned to the enun not the enum value that is 0, using Message.Code.FOO_TRIGGER_SIGNAL.EnumDescriptionToString() from the mentioned wrapper returns A not 0

Message.Code.FOO_TRIGGER_SIGNAL.EnumDescriptionToString()

A

0

3 Answers
3

You cannot have expressions in the case, but you can in the switch, so this will work:

switch (ConvertToMessageCode(msgComingFromFoo[1]))
{
case Message.Code.FOO_TRIGGER_SIGNAL:
break;
}


Where you will need to write ConvertToMessageCode to do the necessary conversion to the Message.Code enum. ConvertToMessageCode just abstracts the necessary conversion details, you may find you do not need a separate method, but can make do with inline code in the switch statement, e.g., a cast.

A case in a switch statement must refer to a constant value. You cannot evaluate an expression in a case.

case

switch

case

To add to @code-apprentice 's answer.

If you're finding the if statement is becoming too long or has multiple conditions within if else's. You can look at refactoring the code and encapsulating your logic into an object and using the visitor pattern to control the work to be done.

if

if else

Something like:

public interface IMessageLogic
{
void ProcessMessage()
}

public class TriggerSignal : IMessageLogic
{
public void ProcessMessage()
{
// Do trigger stuff
}
}

public class FooMessage : IMessageLogic
{
public void ProcessMessage()
{
// Do foo stuff
}
}

public class MessageHandler
{
public void HandleMessage(IMessageLogic messageLogic)
{
messageLogic.ProcessMessage();
}
}

public static void Main()
{
IMessageLogic messageLogic = GetMessage();
var handler = new MessageHandler();

handler.HandleMessage(messageLogic);
}


Visitor Pattern

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