How to avoid “too many parameters” problem in API design?

Question

I have this API function:

public ResultEnum DoSomeAction(string a, string b, DateTime c, OtherEnum d, 
     string e, string f, out Guid code)

Answer 1

In addition to manji response - you may also want to split one operation into several smaller ones. Compare:

 BOOL WINAPI CreateProcess(
   __in_opt     LPCTSTR lpApplicationName,
   __inout_opt  LPTSTR lpCommandLine,
   __in_opt     LPSECURITY_ATTRIBUTES lpProcessAttributes,
   __in_opt     LPSECURITY_ATTRIBUTES lpThreadAttributes,
   __in         BOOL bInheritHandles,
   __in         DWORD dwCreationFlags,
   __in_opt     LPVOID lpEnvironment,
   __in_opt     LPCTSTR lpCurrentDirectory,
   __in         LPSTARTUPINFO lpStartupInfo,
   __out        LPPROCESS_INFORMATION lpProcessInformation
 );

and

 pid_t fork()
 int execvpe(const char *file, char *const argv[], char *const envp[])
 ...

For those who don't know POSIX the creation of child can be as easy as:

pid_t child = fork();
if (child == 0) {
    execl("/bin/echo", "Hello world from child", NULL);
} else if (child != 0) {
    handle_error();
}

Each design choice represent trade-off over what operations it may do.

PS. Yes - it is similar to builder - only in reverse (i.e. on callee side instead of caller). It may or may not be better then builder in this specific case.