How can I make Array.Contains case-insensitive on a string array?

Question

I am using the Array.Contains method on a string array. How can I make that case-insensitive?

Answer 1

array.Contains("str", StringComparer.OrdinalIgnoreCase);

Or depending on the specific circumstance, you might prefer:

array.Contains("str", StringComparer.CurrentCultureIgnoreCase);
array.Contains("str", StringComparer.InvariantCultureIgnoreCase);

Answer 2

Implement a custom IEqualityComparer that takes case-insensitivity into account.

Additionally, check this out. So then (in theory) all you'd have to do is:

myArray.Contains("abc", ProjectionEqualityComparer<string>.Create(a => a.ToLower()))

Answer 3

new[] { "ABC" }.Select(e => e.ToLower()).Contains("abc") // returns true

Answer 4

Some important notes from my side, or at least putting some distributed info at one place- concerning the tip above with a StringComparer like in:

if (array.Contains("str", StringComparer.OrdinalIgnoreCase))
{}

1. array.Contains() is a LINQ extension method and therefore works by standard only with .NET 3.5 or higher, needing:
   using System;
using System.Linq;

2. But: in .NET 2.0 the simple Contains() method (without taking case insensitivity into account) is at least possible like this, with a cast:

   if ( ((IList<string>)mydotNet2Array).Contains(“str”) ) {}

   As the Contains() method is part of the IList interface, this works not only with arrays, but also with lists, etc.