In VB. NET, we can easily obtain the resolution of the monitor. However, it is troublesome to change the resolution of the monitor. Because. net class library does not encapsulate the enumdisplaysettings and changedisplaysettings APIs, but we have to call them. Compared with VB6, VB. net has some minor changes to call API functions!
Next, let's try using these two API functions in VB.net.
Create a new project and add two buttons on form1. One is btngetdisp and the text attribute is set to "get resolution". The other is btnsetdisp and the text attribute is "set resolution ". Then add the following code in the code window:
Private const ccdevicename as short = 32
Private const ccformname as short = 32
Private const dm_pelswidth as integer = & h80000
Private const dm_pelsheight as integer = & h100000
'Refresh frequency constant
Private const dm_displayfrequency as integer = & h400000
'Call an API Function
Private declare function enumdisplaysettings lib "USER32" alias "Enumdisplaysettingsa" (byval lpszdevicename as integer, Byval imodenum as integer, byref lpdevmode as devmode) as Boolean
'Call an API Function
Private declare function changedisplaysettings lib "USER32" alias "Changedisplaysettingsa" (byref lpdevmode as devmode, Byval dwflags as integer) as integer
'Define the structure
Private structure devmode
Public dmdevicename as string
Dim dmspecversion as short
Dim dmdriverversion as short
Dim dmsize as short
Dim dmdriverextra as short
Dim dmfields as integer
Dim dmorientation as short
Dim dmpapersize as short
Dim dmpaperlength as short
Dim dmpaperwidth as short
Dim dmscale as short
Dim dmcopies as short
Dim dmdefaultsource as short
Dim dmprintquality as short
Dim dmcolor as short
Dim dmduplex as short
Dim dmyresolution as short
Dim dmttoption as short
Dim dmcollate as short
Public dmformname as string
Dim dmunusedpadding as short
Dim dmbitsperpel as short
Dim dmpelswidth as integer
Dim dmpelsheight as integer
Dim dmdisplayflags as integer
Dim dmdisplayfrequency as integer
End Structure
'Change resolution, parameter 1 width, parameter 2 height
Private sub changedisp (byref iwidth as single, byref iheight as Single)
Dim blnworked as Boolean
Dim I as integer
Dim devm as form1.devmode
I = 0
Do
Blnworked = enumdisplaysettings (0, I, devm)
I = I + 1
Loop until (blnworked = false)
With devm
. Dmfields = dm_pelswidth or dm_pelsheight or dm_displayfrequency
. Dmpelswidth = iwidth
. Dmpelsheight = iheight
'Refresh frequency is 85
. Dmdisplayfrequency = 85
End
Call changedisplaysettings (devm, 0)
End sub
Private sub btngetdisp_click (byval sender as system. object, Byval e as system. eventargs) handles btngetdisp. Click
Dim X as short = system. Windows. Forms. Screen. primaryscreen. bounds. Width
Dim y as short = system. Windows. Forms. Screen. primaryscreen. bounds. Height
Msgbox ("your display resolution is" & X & "X" & Y)
End sub
Private sub btnsetdisp_click (byval sender as system. object, Byval e as system. eventargs) handles btnsetdisp. Click
If msgbox ("are you sure you want to change the display resolution to 1024x768? ", Msgboxstyle. okcancel, "System message") = msgboxresult. OK then
'The call changes the resolution process
Changedisp (1024,768)
End if
End sub
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The program runs as shown in. Clicking set resolution will change the display resolution to 1024x768 and the refresh frequency to 85. Isn't it easy?
