Code to generate random password

public static string GeneratePassword()
        {
            char tmpChar;
            int idx;
            string password = string.Empty;
            string[] charArray = new string[62];

            for (idx = 0; idx <= 9; idx++)
            {
                charArray[idx] = idx.ToString();
            }

            for (idx = 65; idx <= 90; idx++)
            {
                tmpChar = (char)idx;
                charArray[idx - 55] = tmpChar.ToString();
            }

            for (idx = 97; idx <= 122; idx++)
            {
                tmpChar = (char)idx;
                charArray[idx - 61] = tmpChar.ToString();
            }

            Random randomObj = new Random();
            for (idx = 0; idx < 8; idx++)
            {
                password += charArray[randomObj.Next(62)];
            }

            return password;
        }