Using Drag and Drop in PowerShell GUIs

Drag and drop is a wonderful facility that most of us will use every day without even thinking about it. This article shows how it can be implemented in PowerShell GUI applications.

For this particular script, we’ll implement drag and drop functionality to allow us to drag a file from explorer to a textbox in we’ve created. When the drag and drop operation is complete, the textbox will then show the path to the file.

You can find a copy of the PowerShell Studio form and exported PowerShell code at the PowerShell.Amsterdam repository.

Here is what we our application will do once we have completed it:

To achieve our objective, we need to make use of two events, DragOver, and DragDrop.

DragOver occurs when the mouse is over the control on which we wish to ‘drop’ our object. We’ll typically just use this for changing our pointer to show a move or copy operation is in operation.

DragDrop occurs once the actual operation is finished. That is, the object has been dragged into the form and over the control, and the mouse button released.

To implement this in our application, carry out the following:

  • Create a form
  • Create a Textbox on the form
  • Set the following properties for the Textbox
    • Name : txtDragandDrop
    • Label : Contents dragged:
    • AllowDrop : true

1 - form design and properties

We now define the events that will be processed, and their handlers.

  • DragDrop : txtDragandDrop_DragDrop
  • DragOver : txtDragandDrop_DragOver

2 - form design and events

For the event handler code, use the following :

If you are developing this application in PowerShell Studio, you will need to first export the code, either to a standalone EXE, or .PS1 file.

  • Run the application from either of the above.
  • Drag a file of you choice from explorer to the textbox.

The textbox will be populated with the filepath of the file that has been dragged and dropped over it.

4 - running

Thanks for reading!

Tim

Sharing Events Handlers in PowerShell GUIs

When you setup an event handler and its code, it is helpful to know it can be shared amongst multiple controls whilst still allowing access to the specific control which raised the event.

The first apparent benefit of this is that it instantly reduces the amount of code and code replication in your scripts, but it also gives an insight into what information is received by an event handler.

Although there are some exceptions, a typical event will provide two sets of information that the hander can process

  • The calling object (referenced in your code by use of the variable $this), also known as the Sender
  • The event arguments, passed in as a pipelined object $_

To illustrate how we can use this, we’re going to create a form with two buttons, which share the same event handler, which change the background color to white when the mouse hovers over it, and then back to normal when the mouse leaves the button’s area. You can find a copy of the PowerShell Studio form, and exported .ps1 file (for looking at the pure PowerShell code) at my GitHub repository

  • Create a form with two buttons
  • Select the first button
  • For the MouseHover event, call its handler buttonHover
  • For the MouseLeave event, call its handler buttonLeave
  • Repeat the button setting for the second button
Sharing Events - Force and Event Design

The first buttons configuration

Sharing Events - Force and Event Design Button 2

The second buttons configuration

  For our the event code, use the following:

Shared events in action :

Creating a Shortcut for a Button in a PowerShell GUI

While most of us are all still friends with the mouse in GUIs, keyboard shortcuts once learned are very effective ways of manipulating form controls quicker.

Serveral controls, such as buttons can use keyboard accelerators. This is simply done by prefixing the Text property of the control by an ampersand. By doing this, you can perform the same as the Click event for that control simply by holding down the ALT key on the keyboard, and then the appropriate letter.

For example, a button control with its text property set to &OK will respond to the keyboard combination ALT + O as if the mouse had clicked on it. In keeping with normal Windows functionality, you can identify the keyboard shortcut by holding down the ALT key, and the letter for the accelerator will be listed with an underline.

Here’s how you’d do this in PowerShell Studio :

Keyboard Shortcut

And in PowerShell code itself, this is represented as :