Read binary file using struct to find records

Use %d instead of %ld to print an int

And take a look to Why is “while ( !feof (file) )” always wrong?

A struct haves a fixed size, you can use ftell to get the size of the file and then divide using the size of the struct in order to get the number of records, also, always check the result of those functions.

Something like:

FILE *file;
long size;
size_t count, records;

file = fopen("myfile", "rb");
if (file == NULL) {
    perror("fopen");
    return 0;
}
if (fseek(file, 0, SEEK_END) == -1) {
    perror("fseek");
    return 0;
}
size = ftell(file);
if (size == -1) {
    perror("ftell");
    return 0;
}
if (fseek(file, 0, SEEK_SET) == -1) {
    perror("fseek");
    return 0;
}
records = size / sizeof(x);
for (count = 0; count < records; count++) {
     if (fread(&x, sizeof(x), 1, file) == 1) {
         printf("\n\nID:%d",x.ID); /* %d instead of %ld */
     } else {
         break;
     }
}

But notice that you are always writing to the same variable on the stack.

EDIT:

How do you store the struct in the file?

I'm not storing it, a program is.

If it is not yours (you don't build the file using the same struct) then you can't know which is the sizeof(x) inside the file, read about structure padding and packing.

Use more protection. Test the result of functions.

 FILE *p;
 struct myStruct x;
 p=fopen("myfile","rb");
 assert(p); // Insure file opened

 while(1) {
   size_t n = fread(&x, sizeof(x), 1, p);
   // feof() is insufficient, 
   // fread() can fail due to input errors too and not set end-of-file condition
   // if(feof(p)!=0)
   if (n == 0) {
     break;
   }
   // printf("\n\nID:%ld",x.ID);
   printf("\n\nID:%d", x.ID);  // Use matching specifier
   fflush(stdout); // Insure output occurs promptly
 }
 fclose(p);
 return 0;

Since OP's code had a mis-matched printf specifier, it indicates that either warnings are not fully enabled or OP is using a weak compiler. Suggest fixing that to save time.