C# - Algoritmos - Cadenas Aleatorias (2005, 2008)

using System;
using System.Text;

public string RandomString(int size) {
    StringBuilder builder = new StringBuilder();
    Random random = new Random();
    char ch;
    for (int i = 0; i < size; i++) {
        ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));
        builder.Append(ch);
    }
    return builder.ToString();
}