直线绘制的一个小问题

<P>目的：通过鼠标点击得到两点，量算两点间距离用MessageBox显示（已经成功）；同时，希望在该两点间绘制出一条示意性的直线（失败），代码如下：</P>
<P>if(m_CurrentOperation == Query_Distance ;; Button ==1)<br>{<br>  CString m_Dist_ValueAsString;<br>  CDC *pDC = GetDC();</P>
<P>  if(m_Dist_Click == 0)<br>  {<br>   m_Dist_Line_Start.SetX(X);<br>   m_Dist_Line_Start.SetY(Y);<br>   m_Dist_Start = m_map.ToMapPoint((float)X,(float)Y);<br>   m_Dist_Click = 1;<br>  }<br>  else if(m_Dist_Click == 1)<br>  {<br>   m_Dist_Line_End.SetX(X);<br>   m_Dist_Line_End.SetY(Y);<br>   m_Dist_End = m_map.ToMapPoint((float)X,(float)Y);<br>   m_Dist_Click = 0;<br>   m_Dist_ValueAsString.Format("%f",m_Dist_Start.DistanceTo(m_Dist_End)*1000);<br>   MessageBox(m_Dist_ValueAsString+" m");<br>   pDC->MoveTo((int)m_Dist_Line_Start.GetX(),(int)m_Dist_Line_Start.GetY());<br>   pDC->LineTo((int)m_Dist_Line_End.GetX(),(int)m_Dist_Line_End.GetY());<br>   ReleaseDC(pDC);<br>  }<br>}</P>
<P>请问，哪里有问题了，谢谢！！！</P><img src="images/post/smile/dvbbs/em02.gif" /><img src="images/post/smile/dvbbs/em02.gif" /><img src="images/post/smile/dvbbs/em02.gif" />