控制台应用程序不会自动添加对System.Windows.Forms.dll的引用.

A console application does not automatically add a reference to System.Windows.Forms.dll.

在解决方案资源管理器中右键单击您的项目，然后选择添加引用..."，然后找到System.Windows.Forms并将其添加.

Right-click your project in Solution Explorer and select Add reference... and then find System.Windows.Forms and add it.