using System;
 
public class Test
{
	public static void Main()
	{
		var m1 = DBNull.Value;
        string m2 = null;
 
        string m1Convert = Convert.ToString(m1);
        string m2Convert = Convert.ToString(m2); 
 
        Console.WriteLine( m1Convert ==  String.Empty );
        Console.WriteLine( m2Convert ==  null ); 
 
        string m1Empty = m1 + "";
        string m2Empty = m2 + "";
 
        Console.WriteLine( m1Empty ==  String.Empty );
        Console.WriteLine( m2Empty ==  String.Empty );
	}
}

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