using System;
using System.Text;

public class RandomString
{
	// Generates a random string with a given size.    
	public static string Generate(int size)
	{
		var builder = new StringBuilder(size);

		Random random = new Random();

		// Unicode/ASCII Letters are divided into two blocks
		// (Letters 65–90 / 97–122):
		// The first group containing the uppercase letters and
		// the second group containing the lowercase.  

		// char is a single Unicode character  
		char offsetLowerCase = 'a';
		char offsetUpperCase = 'A';
		const int lettersOffset = 26; // A...Z or a..z: length=26  

		for (var i = 0; i < size; i++)
		{
			char offset;
			if (random.Next(0, 2) == 0)
			{
				offset = offsetLowerCase;
			}
			else
			{
				offset = offsetUpperCase;
			}

			var @char = (char)random.Next(offset, offset + lettersOffset);
			builder.Append(@char);
		}

		return builder.ToString();
	}
}