Hi guys,

I have some problem with external lib.. i try to include external lib into my project but it producing this C2871 error.
C:\Qt\OpenCVProject\20150505_23_Vid\mainwindow.h:9 : error: C2871: 'Videoman' : a namespace with this name does not exist
I already include the related .h file but its still showing the error.. What should i do? Where did i do wrong?

this is my .pro file
Qt Code: 
  1. QT       += core gui opengl xml
  2.  
  3. greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
  4.  
  5. TARGET = uEyeCam
  6. TEMPLATE = app
  7.  
  8.  
  9. SOURCES += main.cpp\
  10.         mainwindow.cpp
  11.  
  12. HEADERS  += mainwindow.h
  13.  
  14. FORMS    += mainwindow.ui
  15.  
  16. win32:CONFIG(release, debug|release): LIBS += -LC:/OpenCV/VideoMan1.1/build/lib/ -lVideoMan
  17. else:win32:CONFIG(debug, debug|release): LIBS += -LC:/OpenCV/VideoMan1.1/build/lib/ -lVideoMand
  18.  
  19. INCLUDEPATH += C:/OpenCV/VideoMan1.1/include
  20. DEPENDPATH += C:/OpenCV/VideoMan1.1/include
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my .h file
Qt Code: 
  1. #include <QMainWindow>
  2. #include "VideoManControl.h"
  3. #include "VideoManInputFormat.h"
  4.  
  5. using namespace std;
  6. using namespace Videoman;
  7.  
  8. namespace Ui {
  9. class MainWindow;
  10. }
  11.  
  12. class MainWindow : public QMainWindow
  13. {
  14.     Q_OBJECT
  15.  
  16. public:
  17.     explicit MainWindow(QWidget *parent = 0);
  18.     ~MainWindow();
  19.  
  20. private slots:
  21.     void on_displayButton_clicked();
  22.     void openCamera();
  23.  
  24. private:
  25.     Ui::MainWindow *ui;
  26. };
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and VideoManControl.h file
Qt Code: 
  1. #ifndef VIDEOMANCONTROL_H
  2. #define VIDEOMANCONTROL_H
  3.  
  4. #ifdef WIN32
  5. #ifdef VideoMan_EXPORTS
  6. #define VIDEOMAN_API __declspec(dllexport)
  7. #else
  8. #define VIDEOMAN_API __declspec(dllimport)
  9. #endif
  10. #endif
  11. #ifdef linux
  12. #define VIDEOMAN_API 
  13. #endif
  14.  
  15. #include "VideoManInputFormat.h"
  16.  
  17. namespace VideoManPrivate
  18. {
  19. 	class VideoManControlPrivate;
  20. 	class VideoManInputController;
  21. };
  22.  
  23. namespace VideoMan
  24. {
  25. ///////---------related code-------------///////
  26. };
  27. #endif
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thanks in advance..