2_RA

C#

Since C# is C-style language, we can deduce that Program.cs contains the entry point of the application. There Application [1] class invokes method Run() [2]

Application.Run(<Window form>)

which opens a specified window (in our case invokes constructor Lesson1).

Application.Run(new Lesson1())

After that constructor invokes the InitializeComponent()

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VB.net

In case of VB.net, there is a similiar type of file Application.Designer.vb. It stores information related to Windows Forms applications such as the authentication mode and the shutdown mode [9]. Here we can see that it overrides the function

OnCreateMainForm() [3]

Which sets and configures the Mainform [4] of the current application to a specified one

Me.Mainform = Global.VBLesson1.VBLesson1

The method OnCreateMainForm() [3] is usually called by OnRun() [5], which according to definition

By default, this method does nothing. However, when you select a main form for your application in the Visual Basic Project Designer, the designer overrides the OnCreateMainForm method with a method that sets the MainForm property to a new instance of the main form [5].

Then, we can the class definition of the Lesson1, where there is

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()>

Which is a part of [7], where DesignerGenerated() defined as

When applied to a class, the compiler implicitly calls a component-initializing method from the default synthetic constructor [6].

DesignerGenerated() automatically adds the call to the InitializeComponent() to the the constructor which will invoke the InitializeComponent() when the form is inialized [6, 8].

Thus, it is quite similiar procedure for both C# and VB.net.

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References

1. https://docs.microsoft.com/en-us/dotnet/api/system.windows.application?view=netcore-3.1

2. https://docs.microsoft.com/en-us/dotnet/api/system.windows.application.run?view=netcore-3.1#System_Windows_Application_Run

3. https://docs.microsoft.com/en-us/dotnet/api/microsoft.visualbasic.applicationservices.windowsformsapplicationbase.oncreatemainform?view=netframework-4.8

4. https://docs.microsoft.com/en-us/dotnet/api/microsoft.visualbasic.applicationservices.windowsformsapplicationbase.mainform?view=netframework-4.8

5. https://docs.microsoft.com/en-us/dotnet/api/microsoft.visualbasic.applicationservices.windowsformsapplicationbase.onrun?view=netframework-4.8

6. https://docs.microsoft.com/en-us/dotnet/api/microsoft.visualbasic.compilerservices.designergeneratedattribute?view=netcore-3.1

7. https://docs.microsoft.com/en-us/dotnet/api/microsoft.visualbasic.compilerservices?view=netcore-3.1

8. https://stackoverflow.com/questions/4573596/vb-net-where-is-default-constructor-of-a-windows-form

9. https://www.informit.com/articles/article.aspx?p=1602817&seqNum=3