how can I temporarily blank a Windows-7 2nd display monitor, in C#? -

i try setting width , height 0 using changedisplaysettingsex, blanks display monitor, when set w , h (and restore dmposition.x) stays off.

my system has 2 monitors, , i'm trying temporarily blank 1 of them. later, need turn on.

here's code.................

    public static void set_monitor_settings( int devnum, bool monitor_on_off )      {         if( monitor_on_off )             console.writeline("turn on ultrasound monitor");         else             console.writeline("turn off ultrasound monitor");          // init:             display_device lpdisplaydevice = new display_device(0);     // out             display_device monitor_name = new display_device(0);        // out             devmode display_setting = new devmode();             lpdisplaydevice.cb = marshal.sizeof(lpdisplaydevice);             display_setting.dmsize = (ushort)marshal.sizeof(display_setting);          // set lpdisplaydevice select 2nd display device:             enumdisplaydevices(null, devnum, ref lpdisplaydevice, 0);                 console.writeline("\ndevnum =" + devnum);                 console.writeline("cb =" + lpdisplaydevice.cb);                 console.writeline("deviceid =" + lpdisplaydevice.deviceid);                 console.writeline("devicekey =" + lpdisplaydevice.devicekey);                 console.writeline("devicename =" + lpdisplaydevice.devicename.trim());                 console.writeline("devicestring =" + lpdisplaydevice.devicestring.trim());          // open settings of 2nd device:         int return_value;         if( monitor_on_off )         {             return_value = enumdisplaysettings(lpdisplaydevice.devicename,                     0,  //enum_current_settings,                                            ///////<<<<<<<<< might need 0                     ref display_setting) ;         }         else         {             return_value = enumdisplaysettings(lpdisplaydevice.devicename,                     enum_current_settings,                                          ///////<<<<<<<<< might need 0                     ref display_setting);         }         if(return_value > 0)// succeeded         {             console.writeline("current mode:\n\t" +                 "{0}w {1}h, " +                 "{2} bit, " +                 "{3} degrees, " +                 "{4} hertz",                 display_setting.dmpelswidth,                 display_setting.dmpelsheight,                 display_setting.dmbitsperpel,                 display_setting.dmdisplayorientation * 90,                 display_setting.dmdisplayfrequency);              //console.writeline(display_setting.dmdisplayorientation + "\t = raw orientation");              display_setting.dmdisplayorientation = 0;   // set landscape orientation landscape             //display_setting.dmdisplayorientation = 2;   // set landscape orientation landscape upside down              if (monitor_on_off)             {                 // set resolution g4.1 (april 2013) requirement:                 display_setting.dmpelswidth = 1280;                 display_setting.dmpelsheight = 1024;                 display_setting.dmposition.x = 1200;             }             else             {                 display_setting.dmpelswidth = 0;                 display_setting.dmpelsheight = 0;              }              int iret = changedisplaysettingsex(lpdisplaydevice.devicename, ref display_setting, intptr.zero, cds_updateregistry, intptr.zero);             if (iret == 0)                 console.writeline("successful");             else                 console.writeline(iret + "\t = changedisplaysettingsex return value ");           }         else         {             console.writeline(">>>  enumdisplaysettings  returned 0.  <<<<<<<<<<<<<<");         }     } 

here solution found , used successfully......

    [dllimport("user32.dll")]     static extern intptr sendmessage(intptr hwnd, int msg, intptr wparam, intptr lparam);      private const int wm_syscommand = 0x0112;     private const int sc_monitorpower = 0xf170;     private const int monitorturnon = -1;     private const int monitorshutoff = 2;      //turn them off     public static void turn_off_monitors()     {         form f = new form();          sendmessage(f.handle, wm_syscommand, (intptr)sc_monitorpower, (intptr)monitorshutoff);     }       //turn them on     public static void turn_on_monitors()     {         form f = new form();          sendmessage(f.handle, wm_syscommand, (intptr)sc_monitorpower, (intptr)monitorturnon);     }