请帮助Parallel.ForEach不使用图形 [英] Please help Parallel.ForEach is not working with graphics

问题描述

System.Threading.Tasks.Parallel.ForEach(ktl,rc=>
                           {
                               ++i;

                               g.DrawRectangle(pen, rc);

                               g.DrawString("KN" + i.ToString(), new Font(FontFamily.GenericSansSerif, 10, FontStyle.Bold),
                      new SolidBrush(Color.Blue), rc.X, rc.Y);
                           }
                       );

但是这个工作

but this works

foreach (Rectangle rc in ktl)
                    {

                        ++i;
                        g.DrawRectangle(pen, rc);

                        g.DrawString("KN"+i.ToString(), new Font(FontFamily.GenericSansSerif, 10, FontStyle.Bold),
               new SolidBrush(Color.Blue), rc.X, rc.Y);

                    }

推荐答案

在图形 [ ^ ] - 他们说的类：



此类型的任何公共静态成员都是线程安全的。不保证所有实例成员都是线程安全的。



旁注：实现IDisposable的类的任何对象都应该在使用后进行处理，这可以通过在使用块中使用来实现，这是最容易实现的。 。您应该使用Font和Solidbrush执行此操作。由于它始终是相同的Font和SolidBrush，因此无需在循环的每次迭代中分配新的。

At the bottom of the MSDN-page for the Graphics[^]-class they state:

"Any public static members of this type are thread safe. Any instance members are not guaranteed to be thread safe."

Sidenote: Any object of a class that implements IDisposable should be disposed after use, which can be easiest achieved by using it within a using-block. You should do this with your Font and Solidbrush. As it's always the same Font and SolidBrush, there's no need to allocate a new one in each iteration of your loop anyway.

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