Getting md5 hash code for dll file in c++ - c++

Question

Hi guys i am trying to get dll md5 hash but it is returning same value all the time, what i did wrong?
this dll is already loaded when i am trying to getHash
i am getting hash with getHash() method and calculating it with CalcHash
thnks in advanced.
#define BUFSIZE 1024
#define MD5LEN 16
int CalcHash(HANDLE hFile, char *md5sum)
{
BOOL bResult = FALSE;
HCRYPTPROV hProv = 0;
HCRYPTHASH hHash = 0;
BYTE rgbFile[BUFSIZE];
DWORD cbRead = 0;
BYTE rgbHash[MD5LEN];
DWORD cbHash = 0;
CHAR rgbDigits[] = "0123456789abcdef";
char byt[3];
int rc, err;
rc = CryptAcquireContext(&hProv, NULL, MS_STRONG_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
if(!rc)
{
err = GetLastError();
if(err==0x80090016)
{
//first time using crypto API, need to create a new keyset
rc=CryptAcquireContext(&hProv, NULL, MS_STRONG_PROV, PROV_RSA_FULL, CRYPT_NEWKEYSET);
if(!rc)
{
err=GetLastError();
return 0;
}
}
}
CryptCreateHash(hProv, CALG_MD5, 0, 0, &hHash);
while(bResult = ReadFile(hFile, rgbFile, BUFSIZE, &cbRead, NULL))
{
if (0 == cbRead)
{
break;
}
CryptHashData(hHash, rgbFile, cbRead, 0);
}
cbHash = MD5LEN;
CryptGetHashParam(hHash, HP_HASHVAL, rgbHash, &cbHash, 0);
md5sum[0] = 0;
for (DWORD i = 0; i < cbHash; i++)
{
sprintf(byt, "%c%c", rgbDigits[rgbHash[i] >> 4], rgbDigits[rgbHash[i] & 0xf]);
strcat(md5sum, byt);
}
CryptDestroyHash(hHash);
CryptReleaseContext(hProv, 0);
return 1;
}
char *getHash()
{
CalcHash(L"dsetup.dll", md5sum);
Logger(md5sum);
return md5sum;
}