C#随机生成不重复字符串的两个不错方法

今天整理以前一个项目源码，发现两个随机生成不重复字符串的方法，觉得用起来挺方便的，在此贴出来，方便以后查阅。

方法一：随机生成不重复数字字符串

private int rep=0;

/// <summary>
/// 生成随机数字字符串
/// </summary>
/// <param name="codecount">待生成的位数</param>
/// <returns>生成的数字字符串</returns>
private string generatecheckcodenum(int codecount)
{
string str = string.empty;
long num2 = datetime.now.ticks + this.rep;
this.rep++;
random random = new random(((int)(((ulong)num2) & 0xffffffffl)) | ((int)(num2 >> this.rep)));
for (int i = 0; i < codecount; i++)
{
int num = random.next();
str = str + ((char)(0x30 + ((ushort)(num % 10)))).tostring();
}
return str;
}

方法二：随机生成字符串（数字和字母混和）

/// <summary>
/// 生成随机字母字符串(数字字母混和)
/// </summary>
/// <param name="codecount">待生成的位数</param>
/// <returns>生成的字母字符串</returns>
private string generatecheckcode(int codecount)
{
string str = string.empty;
long num2 = datetime.now.ticks + this.rep;
this.rep++;
random random = new random(((int)(((ulong)num2) & 0xffffffffl)) | ((int)(num2 >> this.rep)));
for (int i = 0; i < codecount; i++)
{
char ch;
int num = random.next();
if ((num % 2) == 0)
{
ch = (char)(0x30 + ((ushort)(num % 10)));
}
else
{
ch = (char)(0x41 + ((ushort)(num % 0x1a)));
}
str = str + ch.tostring();
}
return str;
}