Use string.Contains() with switch()

Question

I\'m doing an C# app where I use

if ((message.Contains(\"test\")))
{
   Console.WriteLine(\"yes\");
} else if ((message.Contains(\"test2\"))) {
   Console.W         


        

Answer 1

Stegmenn nalied it for me but I had one change for when you have an IEnumerbale instead of a string = message like in his example.

private static string GetRoles(IEnumerable<External.Role> roles)
    {
            string[] switchStrings = { "Staff", "Board Member" };
            switch (switchStrings.FirstOrDefault<string>(s => roles.Select(t => t.RoleName).Contains(s)))
            {
                case
                    "Staff":
                    roleNameValues += "Staff,";
                    break;
                case
                    "Board Member":
                    roleNameValues += "Director,";
                    break;
                default:
                    break;
            }

Answer 2

string message = "This is test1";
string[] switchStrings = { "TEST1", "TEST2" };
switch (switchStrings.FirstOrDefault<string>(s => message.ToUpper().Contains(s)))
{
    case "TEST1":
        //Do work
        break;
    case "TEST2":
        //Do work
        break;
    default:
        //Do work
        break; 
}

Answer 3

This will work in C# 8 using a switch expresion

var message = "Some test message";

message = message switch
{
    string a when a.Contains("test") => "yes",
    string b when b.Contains("test2") => "yes for test2",
    _ => "nothing to say"
};

For further references https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/switch-expression

Answer 4

You can do the check at first and then use the switch as you like.

For example:

string str = "parameter"; // test1..test2..test3....

if (!message.Contains(str)) return ;

Then

switch(str)
{
  case "test1" : {} break;
  case "test2" : {} break;
  default : {} break;
}

Answer 5

Faced with this issue when determining an environment, I came up with the following one-liner:

string ActiveEnvironment = localEnv.Contains("LIVE") ? "LIVE" : (localEnv.Contains("TEST") ? "TEST" : (localEnv.Contains("LOCAL") ? "LOCAL" : null));

That way, if it can't find anything in the provided string that matches the "switch" conditions, it gives up and returns null. This could easily be amended to return a different value.

It's not strictly a switch, more a cascading if statement but it's neat and it worked.

Answer 6

Nope, switch statement requires compile time constants. The statement message.Contains("test") can evaluate true or false depending on the message so it is not a constant thus cannot be used as a 'case' for switch statement.