.NET Fiddle

CSharp · Console

/Program.cs

using System;
using System.Linq;
					
public class Program
{
	public static void Main()
	{
		string stringToCheck = "text1text2text3";
		string[] stringArray = { "text1", "someothertext"};

		if(stringArray.Any(a=> String.Equals(a, stringToCheck, StringComparison.InvariantCultureIgnoreCase)) )
		{ 
			Console.WriteLine(true);
		}
		else
		{
			Console.WriteLine(false);
		}
		
		//IndexOf
		if (stringArray.Any(w=> w.IndexOf(stringToCheck, StringComparison.InvariantCultureIgnoreCase)>=0))
		{ 
			Console.WriteLine(true);
		}
		else
		{
			Console.WriteLine(false);
		}
	}
}