C#随机生成用户名

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public static string GetRandomString(int length)
{
string randStr = "";
Random rd = new Random();
byte[] str = new byte[length];
int i;
for (i = 0; i < length-1; i++)
{
int a = 0;
while (!((a >= 48 && a <= 57) || (a >= 97 && a <= 122)))
{
a = rd.Next(48, 122);
}
str[i] = (byte)a;
}
string username = new string(UnicodeEncoding.ASCII.GetChars(str));
Random r = new Random(unchecked((int)DateTime.Now.Ticks));
string s1 = ((char)r.Next(97, 122)).ToString();
username = username.Replace("/0", "");
randStr = s1 + username;
return randStr;
}