Why return only first character when convert cstring to LPCSTR

As already said you need a conversion instead of a casting. The CString class can do that for you:

// Your code assumes a Unicode build and this example too

CString strData1 = L"ABCDE";

// Create a CStringA. 
// The conversion from Unicode to ANSI is done by the CString class.
// May also use CStringA strData1A(strData1);
CStringA strData1A = strData1;

// Get a LPCSTR from the CStringA
LPCSTR spData = strData1A.GetString();

MessageBox(NULL, strData1.GetString(), L"CString strData", MB_OK);

// Create a CString (CStringW) from a LPCSTR with conversion
MessageBox(NULL, CString(spData).GetString(), L"LPCSTR spData", MB_OK);

You should also avoid using C style castings. Use the C++ casting operators instead (see Type conversions - C++ Tutorials[^] and Casting Operators[^]).

one more thing , when you are using function check there should be a function for unicode also..

like in registry there is a function

RegCreateKeyExA

but for Unicode there is another version of same function called

RegCreateKeyExW

Mumtaz Ali