Pen C＃出錯

Question

我做了一個使用鼠標選擇區域的系統。 但是，當我選擇該區域時：

對不起我的英文，我是巴西人......

我的代碼：

    private void ResizeSelection()
    {

        if (CurrentAction == ClickAction.LeftSizing)
        {

            if (Cursor.Position.X < CurrentBottomRight.X - 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentTopLeft.X = Cursor.Position.X;
                RectangleWidth = CurrentBottomRight.X - CurrentTopLeft.X;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }

        }
        if (CurrentAction == ClickAction.TopLeftSizing)
        {

            if (Cursor.Position.X < CurrentBottomRight.X - 10 && Cursor.Position.Y < CurrentBottomRight.Y - 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentTopLeft.X = Cursor.Position.X;
                CurrentTopLeft.Y = Cursor.Position.Y;
                RectangleWidth = CurrentBottomRight.X - CurrentTopLeft.X;
                RectangleHeight = CurrentBottomRight.Y - CurrentTopLeft.Y;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }
        }
        if (CurrentAction == ClickAction.BottomLeftSizing)
        {

            if (Cursor.Position.X < CurrentBottomRight.X - 10 && Cursor.Position.Y > CurrentTopLeft.Y + 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentTopLeft.X = Cursor.Position.X;
                CurrentBottomRight.Y = Cursor.Position.Y;
                RectangleWidth = CurrentBottomRight.X - CurrentTopLeft.X;
                RectangleHeight = CurrentBottomRight.Y - CurrentTopLeft.Y;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }

        }
        if (CurrentAction == ClickAction.RightSizing)
        {

            if (Cursor.Position.X > CurrentTopLeft.X + 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentBottomRight.X = Cursor.Position.X;
                RectangleWidth = CurrentBottomRight.X - CurrentTopLeft.X;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }
        }
        if (CurrentAction == ClickAction.TopRightSizing)
        {

            if (Cursor.Position.X > CurrentTopLeft.X + 10 && Cursor.Position.Y < CurrentBottomRight.Y - 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentBottomRight.X = Cursor.Position.X;
                CurrentTopLeft.Y = Cursor.Position.Y;
                RectangleWidth = CurrentBottomRight.X - CurrentTopLeft.X;
                RectangleHeight = CurrentBottomRight.Y - CurrentTopLeft.Y;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }
        }
        if (CurrentAction == ClickAction.BottomRightSizing)
        {

            if (Cursor.Position.X > CurrentTopLeft.X + 10 && Cursor.Position.Y > CurrentTopLeft.Y + 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentBottomRight.X = Cursor.Position.X;
                CurrentBottomRight.Y = Cursor.Position.Y;
                RectangleWidth = CurrentBottomRight.X - CurrentTopLeft.X;
                RectangleHeight = CurrentBottomRight.Y - CurrentTopLeft.Y;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }
        }
        if (CurrentAction == ClickAction.TopSizing)
        {

            if (Cursor.Position.Y < CurrentBottomRight.Y - 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentTopLeft.Y = Cursor.Position.Y;
                RectangleHeight = CurrentBottomRight.Y - CurrentTopLeft.Y;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }
        }
        if (CurrentAction == ClickAction.BottomSizing)
        {

            if (Cursor.Position.Y > CurrentTopLeft.Y + 10)
            {

                //Erase the previous rectangle
                g.DrawRectangle(EraserPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);
                CurrentBottomRight.Y = Cursor.Position.Y;
                RectangleHeight = CurrentBottomRight.Y - CurrentTopLeft.Y;
                g.DrawRectangle(MyPen, CurrentTopLeft.X, CurrentTopLeft.Y, RectangleWidth, RectangleHeight);

            }

        }

    }

我想知道是否有辦法解決這個問題或使其變得透明，只顯示矩形的邊緣。 謝謝，

Answer 1

你錯了使用Graphics 。

你永遠不應該調用CreateGraphics()來繪制控件; 它將在下一個油漆上被抹去。

相反，您應該處理Paint事件並在每次重繪時繪制所需的所有內容。

當鼠標移動時，調用Invalidate()以強制重繪。