当前的屏幕除任务栏外的工作域大小
    this.Width = System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Width;
    this.Height = System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Height;

当前的屏幕包括任务栏的工作域大小
this.Width=System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width;
this.Height=System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height;

任务栏大小
this.Width=System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width-System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Width;
this.Height=System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height-System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Height;

winform实现全屏显示
WinForm:
this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
this.WindowState = System.Windows.Forms.FormWindowState.Maximized;
this.TopMost = true;