c# memcmp image compare error -

im trying compare 2 smalls blocks of image using memcmp method. saw answer what fastest way can compare 2 equal-size bitmaps determine whether identical? , tried implement in project:

private void form1_load(object sender, eventargs e) {     bitmap prev, curr;      prev = (bitmap) image.fromfile(@"c:\users\public\desktop\b.png");        curr = (bitmap)image.fromfile(@"c:\users\public\desktop\b.png");     messagebox.show(comparememcmp(prev, curr).tostring()); } 

this method-

[dllimport("msvcrt.dll")] private static extern int memcmp(intptr b1, intptr b2, long count);  public static bool comparememcmp(bitmap b1, bitmap b2) {     if ((b1 == null) != (b2 == null)) return false;     if (b1.size != b2.size) return false;      var bd1 = b1.lockbits(new rectangle(new point(0, 0), b1.size), imagelockmode.readonly, pixelformat.format32bppargb);     var bd2 = b2.lockbits(new rectangle(new point(0, 0), b2.size), imagelockmode.readonly, pixelformat.format32bppargb);      try     {         intptr bd1scan0 = bd1.scan0;         intptr bd2scan0 = bd2.scan0;          int stride = bd1.stride;         int len = stride * b1.height;          return memcmp(bd1scan0, bd2scan0, len) == 0;     }         {         b1.unlockbits(bd1);         b2.unlockbits(bd2);     } } 

and im getting error when calling memcmp function

a call pinvoke function 'windowsformsapplication1!windowsformsapplication1.form1::memcmp' has unbalanced stack. because managed pinvoke signature not match unmanaged target signature. check calling convention , parameters of pinvoke signature match target unmanaged signature. 

any idea why happening? did based on answer.

the correct signature is:

[dllimport("msvcrt.dll", callingconvention=callingconvention.cdecl)] static extern int memcmp(intptr b1, intptr b2, intptr count); 

because in c, count size_t, can 32 or 64 bits depending if program running @ 32 or 64 bits.

then use it:

return memcmp(bd1scan0, bd2scan0, (intptr)len) == 0;