Programmatically detect if Mouse and Keyboard are plugged in - vb.net

Question

I was wanting to know what is the best way to detect if a mouse or keyboard is plugged in to the computer? I have an application that is mostly used in a touchscreen standalone but I want to know if there is a keyboard plugged in don't fire off pulling up the windows keyboard or a form that contains a numeric keypad. Then change some behavior if the mouse is plugged in against if it isn't.

Answer 1

Using VB.Net, I would use System.Management (don't forget to add this reference in the Project [Menu] -> Add Reference) ManagementObjectSearcher combined with System.Linq to find the solution like this,
Imports System
Imports System.Management
Imports System.Linq
Public Module Module1
Public Sub Main()
Console.WriteLine(HasDevice("PointingDevice"))
Console.WriteLine(HasDevice("Keyboard"))
Console.ReadKey()
End Sub
Public Function HasDevice(strtype As String)
Dim searcher As New ManagementObjectSearcher("root\CIMV2", "SELECT * FROM Win32_" + strtype)
Dim result = From mobj In searcher.Get()
Select mobj Where mobj("Status").ToString() = 0
Return Not IsNothing(result)
End Function
End Module
Result
You could also hard-coded it to avoid input mistake like TRiNE suggested (though using C#)
Public Function HasPointingDevice()
Dim searcher As New ManagementObjectSearcher("root\CIMV2", "SELECT * FROM Win32_PointingDevice")
Dim result = From mobj In searcher.Get()
Select mobj Where mobj("Status").ToString() = 0
Return Not IsNothing(result)
End Function
Public Function HasKeyboard()
Dim searcher As New ManagementObjectSearcher("root\CIMV2", "SELECT * FROM Win32_Keyboard")
Dim result = From mobj In searcher.Get()
Select mobj Where mobj("Status").ToString() = 0
Return Not IsNothing(result)
End Function
And call them like this
Public Sub Main()
Console.WriteLine(HasPointingDevice())
Console.WriteLine(HasKeyboard())
Console.ReadKey()
End Sub
They will produce the same result

Answer 2

You can use C# System.Management and ManagementObjectSearcher
Here is a sample code. Modify as it matches your need.
public bool isPointingDeviceAttached()
{
ManagementObjectSearcher searcher =
new ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM Win32_PointingDevice");
int devCount = 0;
foreach (ManagementObject obj in searcher.Get()) {
if(obj["Status"].ToString().Contains("OK")) // if device is ready
devCount++;
}
return devCount>0;
}
public bool isKeyboardAttached()
{
ManagementObjectSearcher searcher =
new ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM Win32_Keyboard");
int devCount = 0;
foreach (ManagementObject obj in searcher.Get()) {
if (obj["Status"].ToString().Contains("OK")) // if device is ready
devCount++;
}
return devCount>0;
}
Make sure to add using System.Management; line and to add System.Management in references.
You can use more ManagementObject attributes as match your need. Here is a list of attributes and some other external references.
Pointing device class ref. & attribute list
C#, C++ similar example

Answer 3

I spent a couple of days tackling this and found nothing that says a keyboard is detached. Only what is attached currently. That gave me an idea though! With my keyboard attached I checked and three keyboard devices were listed. I removed the keyboard and one disappeared. Now I just look for obj.tostring.contains("USB") and if it doesn't I know there is no keyboard attached to my tablet.
The other two were HID and ACPI which I guess are the touchscreen and mousepad.
Of course other tablets may be different so it isn't a robust
Edit: TO be clear, using the previous answer's code foreach (ManagementObject obj in searcher.Get()) { if (obj["Status"].ToString().Contains("OK")) // if device is ready devCount++;
I use obj.tostring.contains("USB") instead of (obj["Status"]xxxx If the tablet is plugged in I will get three keyboards listed and all the "Status" variables report OK. If I unplug the keyboard there are only two entries both of which have a status of OK while the USB keyboard status simply isn't there. So I just look for the USB string in the object and if it isn't there then I know it isn't plugged in.