System.InvalidOperationException：对象当前正在其他地方使用

Question

我试图在面板上绘图时似乎出现此错误。我没有C＃的专家，所以希望这里有人能帮助我。提前致谢。

堆栈跟踪显示，

用C

在System.Drawing.Graphics.set_Transform在Victoria.Robotics.Marvin.Teleoperation.MainForm.DrawXYAxis（图形克）（矩阵值）：\用户\ kasunt \微软Robotics Dev Studio 2008 R3 \ Marvin \ Teleoperation \ MainForm.cs：line 2173 at Victoria.Robotics.Marvin.Teleoperation.MainForm.envMap_Paint（Object sender，PaintEventArgs e）in C：\ Users \ kasunt \ Microsoft Robotics Dev Studio 2008 R3 \在System.Windows.Forms的System.Windows.Forms.Control.PaintWithErrorHandling（PaintEventArgs e，Int16图层，布尔disposeEventArgs）System.Windows.Forms.Control.OnPaint（PaintEventArgs e）上的第2143行：Marvin \ Teleoperation \ MainForm.cs： .Control.WmPaint（Message & m）at System.Windows.Forms.Control.WndProc（Message &米）在System.Windows.Forms.ScrollableControl.WndProc（消息& m）上System.Windows.Forms.Control.ControlNativeWindow.OnMessage（消息& m）上System.Windows.Forms.Control.ControlNativeWindow.WndProc（消息& m）在System.Windows.Forms.NativeWindow.Callback（IntPtr hWnd，Int32 msg，IntPtr wparam，IntPtr lparam）

代码如下。错误似乎设置变换时出现，

private void envMap_Paint(object sender, PaintEventArgs e) 
    { 
     DrawXYAxis(e.Graphics); 
    } 

    /// <summary> 
    /// Helper to draw the XY axis and plot the map 
    /// </summary> 
    public void DrawXYAxis(Graphics g) 
    { 
     Rectangle rect = envMap.ClientRectangle; 

     myPen = new Pen(Color.Black, 1); 
     g.PageUnit = GraphicsUnit.Millimeter; 
     g.PageScale = 0.1F; 
     IntPtr hdc = g.GetHdc(); 
     int hMemDC = hdc.ToInt32(); 

     // Reverse the axis of the drawing surface 
     Matrix mx = new Matrix(1, 0, 0, -1, 0, envMap.ClientSize.Height * 2); 
     g.Transform = mx; 
     g.TranslateTransform(50, 100, MatrixOrder.Append); 

     // For drawing X - AXIS 
     g.DrawLine(myPen, 0, 0, (2 * rect.Right - 60), 0); 
     // For drawing Y - AXIS 
     g.DrawLine(myPen, 0, 0, 0, 2 * rect.Bottom); 

     // For drawing Arrow on X-AXIS 
     g.DrawLine(myPen, (2 * rect.Right - 60) - 15, 8, (2 * rect.Right - 60), 0); 
     g.DrawLine(myPen, (2 * rect.Right - 60), 0, (2 * rect.Right - 60) - 15, -8); 

     // For drawing Arrow on Y-AXIS 
     g.DrawLine(myPen, 8, 2 * rect.Bottom - 15, 0, 2 * rect.Bottom); 
     g.DrawLine(myPen, 0, 2 * rect.Bottom, -8, 2 * rect.Bottom - 15); 

     // Save the state to restore later 
     GraphicsState state = g.Save(); 

     // Create a matrix to offset the text to the desired position and flip it the 
     // right way up again 
     Matrix mx2 = new Matrix(1, 0, 0, -1, 0, 0); 
     Matrix mx1 = mx.Clone(); 
     mx1.Multiply(mx2); 
     g.Transform = mx1; 
     SolidBrush drawBrush = new SolidBrush(Color.Black); 
     Font drawFont = new Font("Microsoft Sans Serif", 9, FontStyle.Bold); 
     StringFormat sF = new StringFormat(StringFormatFlags.NoClip); 
     sF.Alignment = StringAlignment.Center; 
     g.DrawString("X", drawFont, drawBrush, (2 * rect.Right - 40), -2 * Font.Height, sF); 
     g.DrawString("Y", drawFont, drawBrush, -40, -(2 * rect.Height + 2 * Font.Height), sF); 

     // Restore state 
     g.Restore(state); 

     drawFont = new Font("Microsoft Sans Serif", 7); 

     // Drawing Tick Marks and Labels 
     // NOTE THE LABELS ON THE AXES WILL CHANGE TO REFFECT THE REAL POSITION OF THE ROBOT.... 
     myPen.Dispose(); 
    } 

线＃2173，

 g.Transform = mx; 

线＃2143，

 DrawXYAxis(e.Graphics); 

Answer 1

这是一个选项通常通过非法使用图形出现异常上下文在另一个线程。我不得不猜测你的程序中还有其他代码也在使用图形。

如果您不知道代码可能是什么，请使用Debug + Windows + Threads并查看列出的线程的调用堆栈。也可以在源代码中查找Control.CheckForIllegalCrossThreadCalls的任何分配。您需要删除该语句，以便在违反线程要求时获得更好的诊断。

Answer 2

原来是因为以下两行，

IntPtr hdc = g.GetHdc(); 
    int hMemDC = hdc.ToInt32();