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Xamarin.Forms using Visual Basic.NET

  • Artikkeli

Xamarin does not support Visual Basic directly - follow the instructions on this page to create a C# Xamarin.Forms solution and then replace the .NET Standard C# project with Visual Basic.

Create a Xamarin.Forms solution and then replace the .NET Standard project with Visual Basic

Note

You must use Visual Studio on Windows to program with Visual Basic.

Xamarin.Forms with Visual Basic walkthrough

Follow these steps to create a simple Xamarin.Forms project that uses Visual Basic:

  1. From Visual Studio 2019 choose Create a new project.

  2. In the Create a new project window, type Xamarin.Forms to filter the list and select Mobile App (Xamarin.Forms), then press Next.

    Filter for Xamarin.Forms apps

  3. On the next screen, type a name for the project and press Create.

  4. Choose the Blank template and press OK:

    Blank Xamarin.Forms template

    This creates a Xamarin.Forms solution in Visual Studio, using C#. The next steps modify the solution to use Visual Basic.

  5. Right-click on the solution and choose Add > New Project...

  6. Type Visual Basic library to filter the project options and choose the Class Library (.NET Standard) option with the Visual Basic icon:

    Filter for Visual Basic library

  7. On the next screen, type a name for the project and press Create.

  8. Right-click on the Visual Basic project and choose Properties, then change the Default namespace to match the existing C# projects:

    Ensure the Visual Basic root namespace matches the Xamarin.Forms app

  9. Right-click on the new Visual Basic project and choose Manage NuGet Packages, then install Xamarin.Forms and close the package manager window.

    Forms and close the package manager window

  10. Rename the default Class1.vb file to App.vb:

    Rename the default Class1 file and class to App

  11. Paste the following code into the App.vb file, which will become the starting point of your Xamarin.Forms app:

    Imports Xamarin.Forms

Public Class App
    Inherits Application

    Public Sub New()
        Dim label = New Label With {.HorizontalTextAlignment = TextAlignment.Center,
                                    .FontSize = Device.GetNamedSize(NamedSize.Medium, GetType(Label)),
                                    .Text = "Welcome to Xamarin.Forms with Visual Basic.NET"}

        Dim stack = New StackLayout With {
            .VerticalOptions = LayoutOptions.Center
        }
        stack.Children.Add(label)

        Dim page = New ContentPage
        page.Content = stack
        MainPage = page

    End Sub

End Class

  12. Update the Android and iOS projects so that they reference new Visual Basic project (and not the C# project created by the template). Right-click on the References node in the Android and iOS projects to open the Reference Manager. Un-tick the C# library and tick the Visual Basic library (don't forget, do this for both the Android and iOS projects).

    Remove old project reference, add Visual Basic reference

  13. Delete the C# project. Add new .vb files to build out your Xamarin.Forms application. A template for new ContentPages in Visual Basic is shown below:

    Imports Xamarin.Forms

Public Class Page2
Inherits ContentPage

    Public Sub New()
        Dim label = New Label With {.HorizontalTextAlignment = TextAlignment.Center,
                                    .FontSize = Device.GetNamedSize(NamedSize.Medium, GetType(Label)),
                                    .Text = "Visual Basic ContentPage"}

        Dim stack = New StackLayout With {
            .VerticalOptions = LayoutOptions.Center
        }
        stack.Children.Add(label)

        Content = stack
    End Sub
End Class

Limitations of Visual Basic in Xamarin.Forms

As stated on the Portable Visual Basic.NET page, Xamarin does not support the Visual Basic language. This means there are some limitations on where you can use Visual Basic:

  • XAML pages cannot be included in the Visual Basic project - the code-behind generator can only build C#. It is possible to include XAML in a separate, referenced, C# portable class library and use databinding to populate the XAML files via Visual Basic models (an example of this is included in the sample).

  • Custom Renderers cannot be written in Visual Basic, they must be written in C# in the native platform projects.

  • Dependency Service implementations cannot be written in Visual Basic, they must be written in C# in the native platform projects.