Using Jot in a VB Application

[SezMe]

I am trying to use Jot in my VB WPF application but there is not a one-to-one correspondence with the C# Demo application. Is such an example available?

[anakic]

I haven't made one as I haven't done much VB.NET programming, but if you paste your code, we can probably figure out if anything is wrong and how to fix it.

[SezMe]

Here is my Services Module:

`Imports Jot

Module TrackingService
`Public Trackr As New Tracker()

`Sub New()

	Trackr.Configure(Of Window)().Id(Function(w) w.Name).Properties(Function(w) New With
			{
			Key w.Height,
			Key w.Width,
			Key w.Left,
			Key w.Top
			}
			).PersistOn(NameOf(Window.Closed))
End Sub

`End Module

There is not a New method for Windows so I have:

Private Sub MainWindow_Initialized(sender As Object, e As EventArgs) Handles Me.Initialized
Trackr.Track(Me)
End Sub

That line throws this error: The type initializer for 'PIM.TrackingService' threw an exception (PIM is the name of my application).

[SezMe]

Yuck! How do I reduce the font size?

[anakic]

What does the exception message say?

[SezMe]

Exception thrown: 'System.ArgumentException' in Jot.dll
Exception thrown: 'System.TypeInitializationException' in PIM.exe

[SezMe]

anakic, do you need any more information from me to try to diagnose the problem?

[anakic]

Hi. It's not going to be easy without giving it a try. In my Visual Studio, I don't have VB.NET windows forms projects available, which probably means I'm missing an installer workload. I'm a bit swamped at the moment, so I don't know when I'll be able to check but I'll leave the issue open so I revisit it when I get the chance.

[SezMe]

I understand - get at this when you can.

To help, I've created a very simple project with only about 10 lines of code. It demonstrates the issue I have run into. See the attached.

I hope that helps.

JotDemo.zip

[anakic]

It looks like with VB.NET the projection of the anonymous type gets wrapped inside a Convert expression by the VB.NET compiler:

Any ideas why VB.NET is casting the result to object instead of keeping the anonymous type? I don't use VB.NET so I'm not sure if it's a syntax thing or just the way the VB.NET compiler is implemented.

Anyway, Jot analyzes the expression and sees the Convert expression rather than the NewExpression that it expects. The NewExpression gets nested inside the Convert expression but Jot does not check there, so it throws an error.

You can get around this by using multiple Property methods calls instead of the Properties method:

Trackr.Configure(Of Window)().Id(Function(w) w.Name, SystemInformation.VirtualScreen.Size) _
            .Property(Function(w) w.Top) _
            .Property(Function(w) w.Left) _
            .Property(Function(w) w.Height) _
            .Property(Function(w) w.Width) _
            .PersistOn(NameOf(Window.Closing)).StopTrackingOn(NameOf(Window.Closing))

The above should work fine.

One more suggestion - for WPF use the SourceInitialized event rather than Loaded to start tracking the window. Load happens after the first render, so if you use it, you'll see the window jump from it's default location to the stored one.

[anakic]

@SezMe did you give the above a try?

[SezMe]

I did, immediately, and wrote it up here but the post is not here! Very Sorry! I'll use your suggestion and give you the results and answer your question right now.

[SezMe]

First, here is why VB.NET is casting the result to an object (see link below):

"The class has no usable name, inherits directly from Object, ...."

Thus, an anonymous type in VB MUST be an object.

When I tried your modifications previously, they did not work thus the longer (missing) write up. Now, however, the approach you suggested works just fine.

Thank you very much.

https://docs.microsoft.com/en-us/dotnet/visual-basic/programming-guide/language-features/objects-and-classes/anonymous-types

[SezMe]

For those who may be reading this who want to use Jot in a VB application, the SystemInformation Class only exists for Windows Forms, but NOT for wpf. In order to use Jot in VB one must use:

Imports System.Windows.Forms

anakic, is there an equivalent Class in wpf Windows that would provide the same functionality as SystemInformation does for Forms

[ElektroStudios]

Jot analyzes the expression and sees the Convert expression rather than the NewExpression that it expects. The NewExpression gets nested inside the Convert expression but Jot does not check there, so it throws an error.

You can get around this by using multiple Property methods calls instead of the Properties method

@anakic thanks for the solution. But from December 2019, I wonder whether the usage of Properties method (the internal logic to analyze the expression) is a thing that could be fixed or improve soon for VB.NET users of JOT?.

[anakic]

This should be solved with the latest commit and in the current NuGet package (2.1.8). You should now be able to use this style of configuring tracking:

.Properties(Function(w) New With
			{
			Key w.Height,
			Key w.Width,
			Key w.Left,
			Key w.Top
			}