in operator in C#

Question

I think there was an in operator in Commodore 128 Basic.
Is there an in operator in c# too?

I mean is there an operator of kind

if(aString in ["a", "b", "c"])  
  Console.Out.WriteLine("aString is 'a', 'b' or 'c'");

Edit1: Currently I need it to decide if an enum value is in a range of some enum values.

Edit2: Thank you all for the Contains() solutions. I will use it in the future. But currently I have a need for enum values. Can I replace the following statement with Contains() or other methods?

public enum MyEnum { A, B, C }

class MyEnumHelper
{
  void IsSpecialSet(MyEnum e)
  {
    return e in [MyEnum.A, MyEnum.C]
  }
}

Edit3: Sorry it was not Basic. I just googled a while and found Turbo Pascal as a candidate where I could saw it. See http://en.wikipedia.org/wiki/Pascal_%28programming_language%29#Set_types

Edit4: Best answers up to now (end of 15 Feb 2012):

• For lists and arrays: accepted answer and all other answers with Contains() solutions
• For Enums: TheKaneda's answer with good list of pros/cons for different extension methods

Solution 1

Try this:

if(new [] {"a", "b", "c"}.Contains(aString))  
    Console.Out.WriteLine("aString is 'a', 'b' or 'c'");

This uses the Contains method to search the array for aString.

Solution 2

Thanks to my Delphi days, I'm also used to its in keyword. For the generic case in C#, I'm using:

public static class Helper
{
    public static bool In<T>(this T t, params T[] args)
    {
      return args.Contains(t);
    }
  }
}

which can be utilized as follows:

  var color = Color.Aqua;
  var b = color.In(Color.Black, Color.Blue);
  b = "hello".In("hello", "world");

Solution 3

You could use an extension method if you want a slightly more fluent way of working so for this example of a customer and customer status:

public enum CustomerStatus
{
    Active,
    Inactive,
    Deleted
}

public class Customer
{
    public CustomerStatus Status { get; set; }
}

Use the following extension method:

public static class EnumExtensions
{
    public static bool In(this Enum value, params Enum[] values)
    {
        return values.Contains(value);
    }
}

to allow you to write code like this:

private void DoSomething()
{
        var customer = new Customer
        {
            Status = CustomerStatus.Active
        };

        if (customer.Status.In(CustomerStatus.Active, CustomerStatus.Inactive))
        {
            // Do something.
        }
}

Solution 4

No. You can come close:

if (new [] { "a", "b", "c" }.Contains(aString))
    Console.Out.WriteLine("aString is 'a', 'b' or 'c'");

Solution 5

The equivelent in C# would be Contains() (assuming you have a list or array of data)

var myStuff = new List<string> { "a", "b", "c" };
var aString = "a";

if(myStuff.Contains(aString)) {
    //Do Stuff
}

As for the in keyword, it has a different use:

var myStuff = new List<string> { "a", "b", "c" };
var aString = "a";

foreach(string str in myStuff) {
    //Iteration 0 = a, 1 = b, 2 = c
}

View more solutions

Comments

[brgerner]

Is there a related solution for enums?

[Brian Driscoll]

@DavidStratton Actually I don't think that's the case.

[Lzh]

But his question is written this way to demonstrate the way the inquirer wants to use the language, not the actual business purposes.

[JimmiTh]

@brgerner: For a bit of syntactic sugar (which has pros and cons), see stackoverflow.com/a/5320727/1169696 - allows you to do if (MyEnumValue.In(MyEnum.First, MyEnum.Second, MyEnum.Third)) { ... }

[brgerner]

@the If it were possible to assign your extension method only to my enumeration it were perfect.

[brgerner]

Thank you! By now the best answer.

[brgerner]

Update to my last comment: Trevor Pilley's answer solves that problem.

[JimmiTh]

Not my extension method, but it is possible. Adding an answer, since it takes space to demonstrate. Don't accept it, though - since we're far from your original question, that wouldn't be "fair".

[Kevin Brock]

A generic extension method would be more useful: public static bool In<T>(this T value, params T[] values) { return values.Contains(value); }.

[Trevor Pilley]

Yes that is true, I made it enum specific as that was what @brgerner asked about. Others have also posted examples using generics.

[Огњен Шобајић]

I am curious how it impacts performance? Does it create an array or something or it's just IEnumerable which should be optimal?