Generate random string

Possible Duplicate:
c# random string generator

I need to generate a random string with a given length. This is my code so far. The problem is the random string is like "RRRRRR" or "SSSSS" The same letter every time. Just when i restart the app the letter change. I need something like "asrDvgDgREGd"

    public string GenerateChar()
    {
        Random random = new Random();

        return Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65))).ToString();
    }

    public string GenerateChar(int count)
    {        
        string randomString = "";

        for (int i = 0; i < count; i++)
        {
            nahodneZnaky += GenerateChar();
        }

        return randomString;
    }