using System;
 
public class Test
{
	public static void Main()
	{
		string s = null;
		if (s == "abc")
		{
			Console.WriteLine("equals abc");
		}
		else if (s == "")
		{
			Console.WriteLine("equals empty");
		}
		else if ("123" == s)
		{
			Console.WriteLine("equals 123");
		}
		else
		{
			Console.WriteLine("not equal");
		}
		s = "";
		string b = null;
		if (s.CompareTo(b) == 0)
		{
			Console.WriteLine("equals null");
		}
		else
		{
			Console.WriteLine("s.CompareTo(b) produces: " + s.CompareTo(b));
		}
	}
}

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