How to Calculate MD5 of xls file in C language

I have made many researches about MD5 of an xls file but my effort seems be in vain I tried to used lirary and recommendation in this link "https://stackoverflow.com/questions/27858288/calculate-md5-for-a-file-in-c-language" but , still give wrong result , can you help me ??

Well I used to answer the link you gave but then the question was closed. The idea is as follows. First read the file into a buffer. You can do this using following function:

unsigned char * readFile(const char *path)
{
    FILE * pFile;
    long lSize;
    unsigned char * buffer;
    size_t result;

    pFile = fopen (path , "rb" );
    if (pFile==NULL) {fputs ("File error",stderr); exit (1);}

    // obtain file size:
    fseek (pFile , 0 , SEEK_END);
    lSize = ftell (pFile);
    rewind (pFile);

    // allocate memory to contain the whole file:
    buffer = malloc (sizeof(char)*lSize);
    if (buffer == NULL) {fputs ("Memory error",stderr); exit (2);}

    // copy the file into the buffer:
    result = fread (buffer,1,lSize,pFile);
    if (result != lSize) {fputs ("Reading error",stderr); exit (3);}


    // terminate
    fclose (pFile);

    return buffer;
}

Read the file

unsigned char * data = readFile("c:\\file.xls");

Then you must apply MD5 on this buffer of data. You can use code similar to the one in that question (though I am not sure which library/implementation of md5 author of that question used). e.g.,

 char hash[64] = {0};
 md5_byte_t digest[16] = {0};
 md5_init(&state);
 md5_append(&state, (const md5_byte_t  *)data, filesize);
 md5_finish(&state,digest);
 int i=0;      
 for(i; i<16; i++)
 {
      snprintf(hash + i*2,sizeof(hash),"%02x",digest[i]);
 }

Now hash should store the hash of the file, encoded in hexadecimal string. ps. Indeed that sample is incorrectly using strlen with binary file. That is why I suggested the readFile method above; that function also contains code to get file size - you can use that code to get file size and then pass the file size to md5_append method.

ps. also don't forget to free data when you are done with it.