Multiple string comparison with C#

Question

Let's say I need to compare if string x is "A", "B", or "C".

With Python, I can use in operator to check this easily.

if x in ["A","B","C"]:
    do something

With C#, I can do

if (String.Compare(x, "A", StringComparison.OrdinalIgnoreCase) || ...)
    do something

Can it be something more similar to Python?

ADDED

I needed to add System.Linq in order to use case insensitive Contain().

using System;
using System.Linq;
using System.Collections.Generic;

class Hello {
    public static void Main() {
        var x = "A";

        var strings = new List<string> {"a", "B", "C"};
        if (strings.Contains(x, StringComparer.OrdinalIgnoreCase)) {
            Console.WriteLine("hello");
        }
    }
}

or

using System;
using System.Linq;
using System.Collections.Generic;

static class Hello {
    public static bool In(this string source, params string[] list)
    {
        if (null == source) throw new ArgumentNullException("source");
        return list.Contains(source, StringComparer.OrdinalIgnoreCase);
    }

    public static void Main() {
        string x = "A";

        if (x.In("a", "B", "C")) {
            Console.WriteLine("hello");
        }
    }
}

score 45 · Accepted Answer · answered May 17 '11 at 17:12

Use Enumerable.Contains<T> which is an extension method on IEnumerable<T>:

var strings = new List<string> { "A", "B", "C" };
string x = // some string
bool contains = strings.Contains(x, StringComparer.OrdinalIgnoreCase);
if(contains) {
    // do something
}

score 42 · Answer 2 · answered May 17 '11 at 17:13

42

if ((new[]{"A","B","C"}).Contains(x, StringComparer.OrdinalIgnoreCase))

answered May 17 '11 at 17:13

adrianm

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That's a beautiful one-liner. :D – DevOpsSauce Nov 30 '17 at 23:09
Trully is a beautiful solution! – myroslav Apr 11 '18 at 19:45
Doesnt compile in VS 2019. it thinks thats a string[] which has no Contains defined. If cast to IList it will work – stonedauwg May 06 '20 at 17:04

score 14 · Answer 3 · edited May 23 '17 at 12:02

Why yes, there's a classic thread here on StackOverflow with an extension method that would do exactly what you're looking for.

A Use For Extension Methods

public static bool In<T>(this T source, params T[] list)
{
  if(null==source) throw new ArgumentNullException("source");
  return list.Contains(source);
}

EDIT in response to comment below: If you are only solely concerned with strings then:

public static bool In(this string source, params string[] list)
{
    if (null == source) throw new ArgumentNullException("source");
    return list.Contains(source, StringComparer.OrdinalIgnoreCase);
}

Which leads to the syntax you're familiar with:

if(x.In("A","B","C"))
{
  // do something....
}

Note, this is pretty much exactly the same as everyone else has posted only in a syntax closest to what you mentioned.

Apart of being brilliant, your answer is the visually cleanest one. C# don't need to be like the language LISP - Lost In Stupid Parentheses, or Lots of Irritating Superfluous Parentheses. (yes, I know the power and "regularity" of LISP, but... this is just an "is a in a, b, c?" situation) — zurcacielos, Sep 03 '20 at 13:28

score 4 · Answer 4 · edited Feb 05 '20 at 10:27

4

List<string> possibleMatches = new List<string>{"A", "B", "C"};
if (possibleMatches.Contains(inputString))
{
  // do something
}

edited Feb 05 '20 at 10:27

Matt

25,467
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answered May 17 '11 at 17:11

Victor Hurdugaci

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score 3 · Answer 5 · answered May 17 '11 at 17:12

3

Sure

var lst = new List<string>() { "A", "B", "C" };
if (lst.Contains(x, StringComparer.OrdinalIgnoreCase) {
   // do something
}

answered May 17 '11 at 17:12

Jimmy

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score 1 · Answer 6 · answered Jan 09 '23 at 16:58

1

Now that C# 9.0 has pattern matching, there's a new, elegant way to do that:

if (x is "A" or "B" or "C") { ... }

Or, if you need case-insensitivity:

if (x.ToUpperInvariant() is "A" or "B" or "C") { ... }

answered Jan 09 '23 at 16:58

Heinzi

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score -1 · Answer 7 · answered May 17 '11 at 17:10

-1

Probably your best bet would be the Select Case (switch in C#) statement.

Edit: Sorry Select Case is VB.NET (my usual language) and it is switch in C#.

answered May 17 '11 at 17:10

Frazell Thomas

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I updated it with the C# command. Wasn't aware of Select Case being limited to VB.NET. – Frazell Thomas May 17 '11 at 17:13
1

what criteria to you use to say using a switch (or select) is "Best"? – Cos Callis May 17 '11 at 17:23

score -2 · Answer 8 · edited Jun 01 '18 at 07:18

There are a couple of approaches to this, I would suggest you do something like:

 private const string _searched = "A|B|C|";
 private void button1_Click(object sender, EventArgs e)
 {
     string search = "B" + "|";
     if (_searched.IndexOf(search) > -1)
     {
         //do something
     }
 }

There are a lot of other ways to handle this, and the larger your search field gets, the more likely using an array, hashtable or collection becomes valueable. As long as your field of possibilities remains small, the use of a simple string is going to be your best performance. All of the overhead of more complex arrays or objects (or arrays of objects...) is unnecessary.

would the drive-by down voter please stand up and be counted? — Cos Callis, May 17 '11 at 17:19

Multiple string comparison with C#

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