C# Markup 2

Enjoy a Flutter-like UI development experience with .NET Hot Reload and the main .NET UI frameworks

• Build .NET applications fully in C#
• Target browsers and native desktop / mobile
• Use existing UI frameworks. Mature or bleeding edge is your choice: WPF, WinUI 3, Uno Platform. Coming: AvaloniaUI, Maui, possibly Blazor.
• Use the built-in MVVM support - or any other update model that supports your UI framework (e.g. ReactiveUI)
• Use for part or all of your application UI
• Designed to handle large UI fast: practically allocation-free, no reflection, efficient C#

No XAML / HTML / JavaScript / CSS required. No engine or layers to get in your way.

NuGet

Chat (if needed, join DotNetEvolution first)

The best place to ask questions or help!

Getting Started

• Getting started with C# Markup 2 for WPF
• Getting started with C# Markup 2 for WinUI 3 and Uno Platform

Looking for C# Markup 1? Find it here

News

April 14, 2022

New 0.8 release: adds ControlTemplate support and Style improvements!

See here and here for the full list of improvements

February 15, 2022

New 0.6 release: adds WPF and many improvements!

See here for the full list of improvements

November 30, 2021

C# Markup 2 announced at UNOCONF 2021!

This first preview targets WinUI 3 and Uno Platform - including browser webassembly - with C# 10 and .NET 6. It supports .NET Hot Reload for a fast inner dev loop.

See the C# Markup 2 announcement at UNOCONF 2021:

Getting started for WPF

1. Clone this repo
2. Open CSharpMarkup.Wpf.Examples.sln and explore the source for the example pages. Note how page markup and page logic are separated in partial class files, and integrated with Build(), Assign() and Invoke().
3. .NET Hot Reload is supported; edit and save the page markup in VS 2022 while debugging to see instant updates
4. To learn how to use C# Markup 2, read the features description below and experiment in the example app
5. To build your own app, reference from a .NET 6 WPF project and create the C# Markup UI windows, pages etc in that project. Note that for existing apps you can reference (WPF / class library) projects that target older .NET versions from the .NET 6 project, so you can add C# Markup UI to your app without having to migrate existing logic and/or WPF UI to .NET 6 and C# 10.

Getting started for WinUI 3 and Uno Platform

First check if your development environment is ready for Uno Platform and/or WinUI 3:

a) If you only want to target Windows desktop with WinUI 3:

• Get started with the Windows App SDK

b) If you also want to target other OS-es with WinUI 3 using Uno Platform:

• Using Visual Studio 2022 on Windows
• Using other IDE's and OS-es

Now you are ready to work with the WinUI 3 and Uno Platform example app:

1. Clone this repo
2. Open CSharpMarkup.WinUI.Examples.sln
3. Explore the example pages in the Examples.Shared project
4. Debug the Examples.Wasm or the Examples.Windows.Desktop project
5. To use hot reload in VS2022 Preview:
   1. Debug the Examples.Windows.Desktop project
   2. Edit the markup
   3. Click in Visual Studio
   4. After the Visual Studio status bar says , click in the app
6. To learn how to use C# Markup 2, read the features description below and experiment in the example app
7. To build your own app, reference from a .NET 6 WinUI 3 project and create the C# Markup UI windows, pages etc in that project. Note that for existing apps you can reference (WinUI 3 / class library) projects that target older .NET versions from the .NET 6 project, so you can add C# Markup UI to your app without having to migrate existing WinUI 3 UI and/or logic to .NET 6 and C# 10.

Features

C# Markup 2 contains a full declarative, fluent API for existing UI frameworks. It surfaces virtually every layout, view and property, including attached properties, and includes full inline documentation that links each markup helper / parameter to the inline documentation for the underlying UI object / property.

The rich UI frameworks that C# Markup 2 surfaces can contain as much as 500+ UI object types. E.g. layouts, views and styles, but also brushes, rich text elements, drawing primitives, transformations, animations, visual states and more. In addition C# Markup offers powerful and concise convenience API's for layout, bindings, convertors, templates and more.

• When targeting Windows Desktop, the WinUI API from the Windows App SDK is surfaced (without any dependency on Uno Platform).
• When targeting Uno Platform, the Uno.WinUI API is surfaced (atm only webassembly is tested, but any Uno target platform that can support .NET 6 and C# 10 should work)
• When targeting WPF, the WPF API is surfaced.

Basic markup anatomy

Layouts, views, properties and property values look like this:

All properties can be set with extension methods: properties defined on the view type or it's base types, as well as attached properties.

Properties that are defined directly on the view type can alternatively be set with named parameters:

This is mainly useful for properties that take primitive types.

Properties that take enum values have extension methods so the enum name does not have to be repeated
(as in TextAlignment: TextAlignment.Center):

Attached property names are prefixed with the defining type plus underscore:

You can set multiple attached property values for the same defining type in one call:

In addition to this, there are convenience overloads for some view types with just the most commonly used parameters:

Property value converters

Implicit converters are provided in the to subnamespace for common property value types:

These are:

• All converters that accept string values, as specified by the UI framework with the TypeConverter attribute
  Note that WinUI 3 Desktop does not use this attribute, but Uno Platform and WPF do.
• Additional manual converters that also accept other types than string, including tuples if more than one value is expected. E.g.:
  
  Allows you to specify:
  Button() .CornerRadius (2.5) or
  Button() .CornerRadius ((2.5, 0, 2.5, 0))

An example using to.Point:

Button() .Background (RadialGradientBrush (Center: (50, 50), GradientOrigin: (100, 50)))

An example using to.TimeSpan and to.Duration:

ColorAnimation (BeginTime: "0:0:5", Duration: 2.5)

In many cases the inline documentation on the to. type describes the supported values and formatting; especially for strings this can avoid guesswork.

Styles

Styles can be assigned like this:

And defined like this:

In WPF you can bind a style setter value (WinUI 3 does not support this):

Templates

A DataTemplate is passed in as a Func<UIElement>:

A ControlTemplate can be created like this:

• The .BindTemplate() method lets you bind template properties to the templated parent
• The targetType parameter is optional
• b here is a null-valued static UI_Button field. In this example it only serves to demonstrate one way to get intellisense when editing binding expressions for a Button; see Binding power for details.

Here is how you can use a ControlTemplate in an implicit or explicit Style:

Enums for Grid rows and columns

You can use enums instead of numbers for Grid rows and colums. This improves readability and saves you from manually renumbering rows and columns when adding/removing/reordering them

Shorthand helpers

Shorthand helpers are included as an alternative to common combinations of markup helpers:

Insert layout children: conditional and Spread

All layouts ignore null values in their children; this makes it possible to have conditional views depending on the value of an expression at page (re) build time.

The Spread helper allows to insert a variable number of children at a specific position in the children list (similar to what Flutter offers).

Binding power

Thanks to the C# 10 CallerArgumentExpression attribute, you don't have to use strings or nameof() to specify binding paths with good performance. Instead you can use C# expressions and enjoy all the goodness that they bring: full intellisense, compiler checked, renaming support :

Note from the intellisense description in above image that the pathExpression parameter supports several convenience binding syntaxes, which allows to:

• Identify the viewmodel part of the expression with parenthesis:
  path expression = viewmodel.path || (viewmodel expression).path, where path can contain . e.g.:
  • .Bind (vm.SelectedTweet) binds to "SelectedTweet"
  • .Bind ((vm.SelectedTweet).Title) binds to "Title"
  • .Bind ((vm.SelectedTweet).Author.Name) binds to "Author.Name"
• Use ? with null-valued type instances to enjoy C# goodness without needing object instances e.g.:
  • .Bind (vm?.SelectedTweet?.Title) binds to "Title"
    Note that using ? can be necessary because the expression will be evaluated at runtime, even though we don't care about it's value; the CallerArgumentExpression attribute supplies an expression string in addition to the expression value.
• You can still pass in string literals
  • .Bind ("SelectedTweet") binds to "SelectedTweet"

Any surrounding ", @ or whitespace characters in pathExpression are ignored

Bind supports almost all functionality that the UI framework offers for binding. In addition, there are many Bind overloads that allows to:

• Omit the property name to bind to the default property of a view type:
  
• Bind with inline conversion:
  
• Bind a command and it's parameter in one go:
  

Page anatomy - separate markup and UI logic

A typical markup page starts like this:

FlutterPage.cs:

using CSharpMarkup.<UI framework name>;
using static CSharpMarkup.<UI framework name>.Helpers;

namespace Examples;

partial class FlutterPage
{
    public void Build() => Content = 

Note the use of partial class; this lets you separate the UI markup from UI logic:

FlutterPage.logic.cs:

using <UI framework namespace>.Controls;

namespace Examples;

public sealed partial class FlutterPage : Page, IBuild
{
    readonly FlutterViewModel vm;

    public FlutterPage()
    {
        InitializeComponent(); // Only needed for WinUI
        DataContext = vm = <obtain viewmodel instance>;
        Build();

IMPORTANT:

• In <page>.cs:
  Include CSharpMarkup.* namespace usings but no UI objectmodel usings.
  You can also use the UI objectmodel safely in <page>.cs; a good practice then is to define a global using TypeName_UI = <UI objectmodel namespace>.TypeName alias in GlobalUsings.cs

• In <page>.logic.cs:
  DO NOT include CSharpMarkup.* namespace usings and DO NOT use CSharpMarkup objects.
  Markup object instances are not safe to use outside of a markup expression (due to performance features - each markup object has a single static instance to prevent allocating an extra object for each view). That is why Assign and Invoke pass the UI object contained in the markup object to the logic, not the markup object itself.

Note at the moment WinUI for Uno Platform still requires that you have a XAML file for a page. It only needs to contain an empty Page element though, and you can move those files out of sight in a folder, e.g. Xaml:

For WinUI 3 Desktop and WPF you can omit the page XAML files.

Integrate UI markup with UI logic

With Assign and Invoke you can integrate UI markup with UI logic:

SearchPage.cs:

SearchPage.logic.cs:

SearchPage.cs:

SearchPage.logic.cs:

Note:
In SearchPage.cs, StackPanel and TextBox are markup object types, while
in SearchPage.logic.cs they are the corresponding UI framework object types

Development workflow tips

Improve markup colorization in Visual Studio

There is no C# Markup IDE extension (yet...) to properly colorize markup, however C# Markup readability can be improved with this workaround in Visual Studio options:

Under Fonts and Colors, copy the color of User Types - Classes to User Members - Methods (with the Custom... button). Now the markup color for views and properties will no longer be the same.

Fast inner dev loop with .NET Hot Reload

Get the fastest inner dev loop for C# Markup 2 by using .NET Hot Reload in Visual Studio 2022 Preview, targeting Windows.Desktop (packaged). Even when you are not targeting Windows, this is good for getting most of your UI build work done as quickly as possible. Switch to other target(s) to finetune and test.

Since at this moment detecting hot reload in WinUI 3 is broken in .NET SDK, a workaround is to conditionally add a hot reload button on your pages for a debug Windows build. The example contains a .WithHotReloadButton() extension method to do this. In the WPF example app a small hot reload handler is included to automatically rebuild the UI on hot reload, so there is no button workaround needed there.