FillEllipse错误

Question

我收到运行此代码的 JIT编译错误

void draw(PaintEventArgs e)
{
     Graphics gr =this.CreateGraphics();
     Pen pen = new Pen(Color.Black, 5);
     int x = 50;
     int y = 50;
     int width = 100;
     int height = 100;
     gr.DrawEllipse(pen, x, y, width, height);
     gr.Dispose();
     SolidBrush brush = new SolidBrush(Color.White);
     gr.FillEllipse(brush, x,y,width,height);
 }

错误说： 系统参数异常：无效参数 FillEllipse（Brush，int32 x，int32 y，int32 width，int 32 height）;

Answer 1

由于您传递的是PaintEventArgs e，您可以并且应该使用其e.Graphics！

既然你没有创造它，就不要处理它！

但是你创建的那些Pens和Brushes应该被处理掉或者更好，在using条款中创建它们！对于SolidBrush，我们可以使用标准Brush，我们无法更改标准void draw(PaintEventArgs e) { Graphics gr = e.Graphics; int x = 50; int y = 50; int width = 100; int height = 100; gr.FillEllipse(Brushes.White, x, y, width, height); using (Pen pen = new Pen(Color.Black, 5) ) gr.DrawEllipse(pen, x, y, width, height); } ，也不得弃置！

为了确保Fill不会覆盖Draw，我已经切换了订单。

所以，试试这个：

DECLARE
   CURSOR cursor_ab IS
      SELECT num_ab FROM abonne;
BEGIN
   OPEN cursor_ab;

   LOOP
      FETCH cursor_ab INTO numeroab;

      EXIT WHEN cursor_ab%NOTFOUND;
      DBMS_OUTPUT.put_line (numeroab);
   END LOOP;

   CLOSE cursor_ab;
END;
/