How To: Get System Power State Name and Flags

A question came up on our forums and so I investigated writing a wrapper for the GetSystemPowerState API function. This allows you to retrieve the power state name, and also a bitmask of flags – Is the backlight on, is the device password protected etc. This is the result in VB.NET. We will add it to the wish list for the next version of the library.

<DllImport(“coredll.dll”)> _
Public Shared Function GetSystemPowerState(ByVal pBuffer As System.Text.StringBuilder, ByVal Length As Integer, ByRef pFlags As PowerState) As Integer
End Function

<Flags()> _
Public Enum PowerState
[On] = &H10000 ‘// on state
Off = &H20000 ‘ // no power, full off
Critical = &H40000 ‘// critical off
Boot = &H80000 ‘ // boot state
Idle = &H100000 ‘ // idle state
Suspend = &H200000 ‘ // suspend state
Unattended = &H400000 ‘ // Unattended state.
Reset = &H800000 ‘ // reset state
UserIdle = &H1000000 ‘ // user idle state
BackLightOn = &H2000000 ‘ // device screen backlight on
Password = &H10000000 ‘ // This state is password protected.
End Enum

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim sb As New System.Text.StringBuilder(260)
Dim flags As PowerState = 0
Dim ret As Integer = GetSystemPowerState(sb, sb.Capacity, flags)

TextBox1.Text = sb.ToString()
TextBox2.Text = flags.ToString()
End Sub

The last method is just a very simple example of calling the function and displaying the result.

By Peter Freeman Foot

Microsoft Windows Development MVP