asp.net 随机数

/// <summary>
/// 产生随机数
/// </summary>
/// <param name="length"></param>
/// <returns></returns>
public static string GenerateRandomString(int length)
{
System.Text.StringBuilder MyStringBuilder = new System.Text.StringBuilder();
char[] chars = "0123456789 ".ToCharArray();
int index;
Random rnd = new Random();
for (int i = 0; i < length; i++)
{
index = rnd.Next(chars.Length);
MyStringBuilder.Append(chars[index].ToString());
}
return MyStringBuilder.ToString();
}