conversion of C into c# (i'm really stumped)

[C# Programming]

perhaps someone can make a suggestion on how to convert this sample C code into c#?...

C code:

#include
long Now;
struct tm *TimeStruct;
char *TimeString = "000000";
char LabelString[256];
TimeStruct = localtime(&Now)

sprintf(LabelString + strlen(LabelString),"%03d%d%04d",TimeStruct->tm_yday+1,TimeStruct->tm_year%10,Serial);

The issue is that I am working on the barcode command using c# and the variable to be:

string barCodeCommand;

I'm stumped on how to convert this into c# with the timestruct. I'm on with Serial variable.