Authored in 2010

When you want to make your application do things by the user pressing a hotkey / key combination, even when your application does not have focus, you will need a so called global hotkey. A global hotkey is a form of 'keyboard hook' which is a low level way of monitoring the computer for a certain key combination, aka hotkey. Below is a simple class, which let's you register a hotkey and define what code should execute, once the hotkey is pressed.

Using SendInput of User32.dll. Rate this.NET. I am using Windows 10 with Visual Studio 2015 net 4.6 and coding in vb and wpf. Existing code of keybdevent of user32.dll works fine in visual studio 2010. Shared Sub keybdevent(bVk As Byte, bScan As Byte, dwFlags As UInteger, dwExtraInfo As Integer) End Sub After.

To register a hotkey, you need to call the registerHotkey function of the class Hotkey. If you for example want to register ALT+Q, you can do the following:

The first parameter is the sourceform, essentially your main form. The second parameter is a number ID for the hotkey registration, this can be any integer though with some limitations. Next parameter is the key that needs to be pressed, and the fourth and final is the modifier (alt, shift, control, winkey) if any. For this to work, you will need to add one piece of code to your source form:

The above sub captures and sends keyboard messages from the WinAPI to the handleHotKey method in the Hotkey class.

Once you have called Hotkey.RegisterHotkey from your code, the hotkey is registered, and will trigger the code in the Hotkey.handleHotKeyEvent, every time the user presses that specific hotkey.

Note Hotkeys with special keys such as F1-F12, space and similar requires a slightly different approach. The methods are essentially the same, but you will need to retrieve the 'virtual key code' of the special key, and use it as a parameter in the Hotkey.registerHotkey method instead of the Asc(triggerKey.toUpper) parameter. Googling 'virtual key codes' will get you a list of the codes.

Multiple hotkeys

In the above, we assume only one hotkey is needed. Sometimes you need more than one hotkey. In this case we need a few, small changes to the above code. If you examine our 'registerHotkey' method in the Hotkey class, you will notice that the second parameter is a number, in our case '1':

This is an ID for the hotkey we are registering. To add multiple hotkeys we simply need to specify another ID. Let's change our method, so it is possible to manually supply an ID:

Now, when you call the registerHotkey method in the Hotkey class, you will have to supply a hotkeyID of type integer. This allows you to register multiple hotkeys, using a different ID for each. To register three different hotkeys, you might now use the following method call outside the Hotkey class (for example inside a button.click event:

The above will register both ALT+W, ALT+E and ALT+R as hotkeys. Next, we need to add a little more code to the Hotkey class, in order to handle these different hotkeys. We will handle this using a simple Select Case statement on the hotkey ID. Open the Hotkey class and change the 'handleHotKeyEvent' method to reflect the following:

To unregister the hotkeys, when closing your application you'd just change the 'unregisterHotkeys' method with all the registered hotkey ID's:

Bhagavatam telugu serial title song youtube. Those relative minor changes is all there is to handling multiple hotkeys in your .NET application.

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As we mentioned in the previous chapter, Sub procedures are procedures that do not return any value. We have been using the Sub procedure Main in all our examples. We have been writing console applications so far in these tutorials. When these applications start, the control goes to the Main Sub procedure, and it in turn, runs any other statements constituting the body of the program.

Defining Sub Procedures

The Sub statement is used to declare the name, parameter and the body of a sub procedure. The syntax for the Sub statement is −

Where,

• Modifiers − specify the access level of the procedure; possible values are - Public, Private, Protected, Friend, Protected Friend and information regarding overloading, overriding, sharing, and shadowing.

• SubName − indicates the name of the Sub

• ParameterList − specifies the list of the parameters

Example

The following example demonstrates a Sub procedure CalculatePay that takes two parameters hours and wages and displays the total pay of an employee −

When the above code is compiled and executed, it produces the following result −

Passing Parameters by Value

This is the default mechanism for passing parameters to a method. In this mechanism, when a method is called, a new storage location is created for each value parameter. The values of the actual parameters are copied into them. So, the changes made to the parameter inside the method have no effect on the argument.

In VB.Net, you declare the reference parameters using the ByVal keyword. The following example demonstrates the concept −

When the above code is compiled and executed, it produces the following result −

It shows that there is no change in the values though they had been changed inside the function.

Passing Parameters by Reference

A reference parameter is a reference to a memory location of a variable. When you pass parameters by reference, unlike value parameters, a new storage location is not created for these parameters. The reference parameters represent the same memory location as the actual parameters that are supplied to the method.

In VB.Net, you declare the reference parameters using the ByRef keyword. The following example demonstrates this −

When the above code is compiled and executed, it produces the following result −