求教MFC一个简单的问题

Question

下面程序中的这句：if ( BST_CHECKED == IsDlgButtonChecked( IDB_BUTTON5 ) )，什么意思，有什么用，貌似没什么用吧   if ( BST_CHECKED == IsDlgButtonChecked( IDB_BUTTON5 ) )
 {
        //时域坐标纵轴标示
     dcMem.TextOut(5,38,"3E-13",5);
     dcMem.TextOut(5,68,"1.5E-13",7);
     dcMem.TextOut(10,98,"0E+0",4);
     dcMem.TextOut(0,128,"-1.5E-13",8);
     dcMem.TextOut(10,188,"0E+0",4);
     dcMem.TextOut(0,218,"-1.5E-13",8);
     dcMem.TextOut(10,248,"0E+0",4);
     dcMem.TextOut(0,278,"-1.5E-13",8);
        //时域坐标横轴标示
     dcMem.TextOut(40,295,"0E+0",4);
     dcMem.TextOut(80,295,"1E-6",4);
     dcMem.TextOut(440,295,"1E-5",4);
     dcMem.TextOut(840,295,"2E-5",4);
        //相位噪声谱横轴
     dcMem.TextOut(40,600,"1E+3",4);
     dcMem.TextOut(40+int(430/(log10(2)+4)),600,"1E+4",4);
     dcMem.TextOut(40+int(860/(log10(2)+4)),600,"1E+5",4);
     dcMem.TextOut(40+int(1290/(log10(2)+4)),600,"1E+6",4);
     dcMem.TextOut(40+int(1720/(log10(2)+4)),600,"1E+7",4);
        //相位噪声谱纵轴
     dcMem.TextOut(5,485,"1E-13",5);
     dcMem.TextOut(5,455,"1E-11",5);
     dcMem.TextOut(5,425,"1E-9",4);
     dcMem.TextOut(5,395,"1E-7",4);

Answer 1

BST_CHECKED:表示按钮IDB_BUTTON5 被选中

Answer 2

有用的 MSDN 上说的很清楚:
 
The IsDlgButtonChecked function determines whether a button control has a check  next to it or whether a three-state button control is grayed, checked, or neither. 

Answer 3

IsDlgButtonChecked判断button控件是否被选中

Answer 4

BST_CHECKED == IsDlgButtonChecked( IDB_BUTTON5 ) //如果IsDlgButtonChecked的返回值是否为BST_CHECKED
IsDlgButtonChecked对控件IDB_BUTTON5检查是否选中