I did my work in visual studio 2010 c++ console , but now i am trying to convert my work into windows app (making interface of it) in visual studio c++ . For that i have to add some header files which i have to add manually in windows form application, like and it show me some error's in it like DetectRegions.h(10): error C2146: syntax error : missing ';' before identifier 'filename' DetectRegions.h(10): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int DetectRegions.h(10): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int DetectRegions.h(11): error C2061: syntax error : identifier 'string' DetectRegions.h(14): error C2143: syntax error : missing ';' before '<' DetectRegions.h(14): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int DetectRegions.h(14): error C2238: unexpected token(s) preceding ';' DetectRegions.h(16): error C2143: syntax error : missing ';' before '<' DetectRegions.h(16): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int DetectRegions.h(16): error C2238: unexpected token(s) preceding ';' DetectRegions.h(17): error C2061: syntax error : identifier 'RotatedRect' DetectRegions.h(18): error C2653: 'cv' : is not a class or namespace name DetectRegions.h(18): error C2146: syntax error : missing ';' before identifier 'histeq' DetectRegions.h(18): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int DetectRegions.h(18): error C2061: syntax error : identifier 'Mat' DetectRegions.h(18): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int DetectRegions.h(18): warning C4183: 'histeq': missing return type; assumed to be a member function returning 'int' Plate.h is same like DetectRegions.h I add the other headers of opencv in Form1.h like #include "opencv2/features2d/features2d.hpp" #include <opencv/highgui.h> #include "opencv2/opencv.hpp" .......