How to convert a LPCWSTR aka const(wchar)* to string

[Vinod K Chandran via Digitalmars-d-learn]

Hi all.
I want to convert an LPCWSTR to string.
I have a struct like this
```cpp
typedef struct tagNMDATETIMESTRINGW {
  NMHDR      nmhdr;
  LPCWSTR    pszUserString;
  SYSTEMTIME st;
  DWORD      dwFlags;
} NMDATETIMESTRINGW, *LPNMDATETIMESTRINGW;
```
I want to convert this `pszUserString` to a string. How to do it. 
Thanks in advance.