C#随机生成数字、字母

产生62位内任意数字大小写字母的随机数
private static char[] constant=
{
'0','1','2','3','4','5','6','7','8','9',
'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
};
public static string GenerateRandom(int Length)
{
System.Text.StringBuilder newRandom = new System.Text.StringBuilder(62);
Random rd= new Random();
for(int i=0;i<Length;i++)
{
newRandom.Append(constant[rd.Next(62)]);
}
return newRandom.ToString();
}

要是只要字母，改为如下：
private static char[] constant=
{
'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
};
public static string GenerateRandom(int Length)
{
System.Text.StringBuilder newRandom = new System.Text.StringBuilder(52);
Random rd= new Random();
for(int i=0;i<Length;i++)
{
newRandom.Append(constant[rd.Next(52)]);
}
return newRandom.ToString();
}

//调用---------------
sting str=GenerateRandom(6);