C # random generation of non-repeated strings

Today, I sorted out the source code of a previous project and found two methods to randomly generate non-repeated strings. I think it is very convenient to use them. I will post them here for future reference.

Method 1: generate a random string without repeated numbers

Private int rep = 0;

/// <Summary>
/// Generate a random number string
/// </Summary>
/// <Param name = "codecount"> Number of digits to be generated </param>
/// <Returns> the generated numeric string </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) & 0 xffffffffl) | (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;
}

Method 2: generate a random string (mixed digits and letters)

/// <Summary>
/// Generate random character strings (mixed numbers and letters)
/// </Summary>
/// <Param name = "codecount"> Number of digits to be generated </param>
/// <Returns> generated letter string </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) & 0 xffffffffl) | (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;
}