maui-data-binding

Name: maui-data-binding
Author: managedcode

461stars35forks

How to install maui-data-binding?

managedcode/dotnet-skills/maui-data-binding

$npx -y skills add managedcode/dotnet-skills --skill maui-data-binding

Installs into the current project.

Summary

Guidance for .NET MAUI XAML and C# data bindings — compiled bindings, INotifyPropertyChanged / ObservableObject, value converters, binding modes, multi-binding, relative bindings, fallbacks, and MVVM best practices. USE FOR: setting up compiled bindings with x:DataType, implement

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SKILL.md

1	# .NET MAUI Data Binding
2
3	Wire UI controls to ViewModel properties with compile-time safety, correct
4	change notification, and minimal overhead. Prefer compiled bindings everywhere
5	and treat binding warnings as build errors.
6
7	## When to Use
8
9	- Adding `x:DataType` compiled bindings to a new or existing page
10	- Implementing `INotifyPropertyChanged` or CommunityToolkit `ObservableObject`
11	- Creating or consuming `IValueConverter` / `IMultiValueConverter`
12	- Choosing the correct `BindingMode` for a control property
13	- Setting `BindingContext` in XAML or code-behind
14	- Using relative bindings (`Self`, `AncestorType`, `TemplatedParent`)
15	- Applying `StringFormat`, `FallbackValue`, or `TargetNullValue`
16	- Writing AOT-safe code bindings with `SetBinding` and lambdas (.NET 9+)
17
18	## When Not to Use
19
20	- CollectionView layouts / templates — use the `maui-collectionview` skill
21	- Shell navigation parameters — use the `maui-shell-navigation` skill
22	- Service registration / DI — use the `maui-dependency-injection` skill
23	- Property-change-triggered animations — use built-in [.NET MAUI animation APIs](https://learn.microsoft.com/dotnet/maui/user-interface/animation/basic)
24
25	## Inputs
26
27	- A .NET MAUI project targeting .NET 8 or later
28	- XAML pages or C# code-behind where bindings are declared
29	- A ViewModel class (or plan to create one)
30
31	---
32
33	## Compiled Bindings — x:DataType Placement
34
35	Compiled bindings are 8–20× faster than reflection-based bindings and are
36	required for NativeAOT / trimming. Enable them with `x:DataType`.
37
38	### Placement rules
39
40	Set `x:DataType` only where `BindingContext` is set:
41
42	1. Page / View root — where you assign `BindingContext`.
43	2. DataTemplate — which creates a new binding scope.
44
45	Do not scatter `x:DataType` on arbitrary child elements. Adding
46	`x:DataType="x:Object"` on children to escape compiled bindings is an
47	anti-pattern — it disables compile-time checking and reintroduces reflection.
48
49	```xml
50	<!-- ✅ Correct: x:DataType at the page root -->
51	<ContentPage xmlns:vm="clr-namespace:MyApp.ViewModels"
52	x:DataType="vm:MainViewModel">
53	<StackLayout>
54	<Label Text="{Binding Title}" />
55	<Slider Value="{Binding Progress}" />
56	</StackLayout>
57	</ContentPage>
58
59	<!-- ❌ Wrong: x:DataType scattered on children -->
60	<ContentPage x:DataType="vm:MainViewModel">
61	<StackLayout>
62	<Label Text="{Binding Title}" />
63	<Slider x:DataType="x:Object" Value="{Binding Progress}" />
64	</StackLayout>
65	</ContentPage>
66	```
67
68	### DataTemplate always needs its own x:DataType
69
70	```xml
71	<CollectionView ItemsSource="{Binding People}">
72	<CollectionView.ItemTemplate>
73	<DataTemplate x:DataType="model:Person">
74	<Label Text="{Binding FullName}" />
75	</DataTemplate>
76	</CollectionView.ItemTemplate>
77	</CollectionView>
78	```
79
80	### Enforce binding warnings as errors
81
82	\| Warning \| Meaning \|
83	\|---------\|---------\|
84	\| XC0022 \| Binding path not found on the declared `x:DataType` \|
85	\| XC0023 \| Property is not bindable \|
86	\| XC0024 \| `x:DataType` type not found \|
87	\| XC0025 \| Binding used without `x:DataType` (non-compiled fallback) \|
88
89	Add to the `.csproj`:
90
91	```xml
92	<WarningsAsErrors>XC0022;XC0025</WarningsAsErrors>
93	```
94
95	---
96
97	## Binding Modes
98
99	Set `Mode` explicitly only when overriding the default. Most properties
100	already have the correct default:
101
102	\| Mode \| Direction \| Use case \|
103	\|------\|-----------\|----------\|
104	\| `OneWay` \| Source → Target \| Display-only (default for most properties) \|
105	\| `TwoWay` \| Source ↔ Target \| Editable controls (`Entry.Text`, `Switch.IsToggled`) \|
106	\| `OneWayToSource` \| Target → Source \| Read user input without pushing back to UI \|
107	\| `OneTime` \| Source → Target (once) \| Static values; no change-tracking overhead \|
108
109	```xml
110	<!-- ✅ Defaults — omit Mode -->
111	<Label Text="{Binding Score}" />
112	<Entry Text="{Binding UserName}" />
113	<Switch IsToggled="{Binding DarkMode}" />
114
115	<!-- ✅ Override only when needed -->
116	<Label Text="{Binding Title, Mode=OneTime}" />
117	<Entry Text="{Binding SearchQuery, Mode=OneWayToSource}" />
118
119	<!-- ❌ Redundan

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maui-data-binding

461stars35forks

View on GitHub

How to install maui-data-binding?

managedcode/dotnet-skills/maui-data-binding

$npx -y skills add managedcode/dotnet-skills --skill maui-data-binding

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# .NET MAUI Data Binding
2
3	Wire UI controls to ViewModel properties with compile-time safety, correct
4	change notification, and minimal overhead. Prefer compiled bindings everywhere
5	and treat binding warnings as build errors.
6
7	## When to Use
8
9	- Adding `x:DataType` compiled bindings to a new or existing page
10	- Implementing `INotifyPropertyChanged` or CommunityToolkit `ObservableObject`
11	- Creating or consuming `IValueConverter` / `IMultiValueConverter`
12	- Choosing the correct `BindingMode` for a control property
13	- Setting `BindingContext` in XAML or code-behind
14	- Using relative bindings (`Self`, `AncestorType`, `TemplatedParent`)
15	- Applying `StringFormat`, `FallbackValue`, or `TargetNullValue`
16	- Writing AOT-safe code bindings with `SetBinding` and lambdas (.NET 9+)
17
18	## When Not to Use
19
20	- CollectionView layouts / templates — use the `maui-collectionview` skill
21	- Shell navigation parameters — use the `maui-shell-navigation` skill
22	- Service registration / DI — use the `maui-dependency-injection` skill
23	- Property-change-triggered animations — use built-in [.NET MAUI animation APIs](https://learn.microsoft.com/dotnet/maui/user-interface/animation/basic)
24
25	## Inputs
26
27	- A .NET MAUI project targeting .NET 8 or later
28	- XAML pages or C# code-behind where bindings are declared
29	- A ViewModel class (or plan to create one)
30
31	---
32
33	## Compiled Bindings — x:DataType Placement
34
35	Compiled bindings are 8–20× faster than reflection-based bindings and are
36	required for NativeAOT / trimming. Enable them with `x:DataType`.
37
38	### Placement rules
39
40	Set `x:DataType` only where `BindingContext` is set:
41
42	1. Page / View root — where you assign `BindingContext`.
43	2. DataTemplate — which creates a new binding scope.
44
45	Do not scatter `x:DataType` on arbitrary child elements. Adding
46	`x:DataType="x:Object"` on children to escape compiled bindings is an
47	anti-pattern — it disables compile-time checking and reintroduces reflection.
48
49	```xml
50	<!-- ✅ Correct: x:DataType at the page root -->
51	<ContentPage xmlns:vm="clr-namespace:MyApp.ViewModels"
52	x:DataType="vm:MainViewModel">
53	<StackLayout>
54	<Label Text="{Binding Title}" />
55	<Slider Value="{Binding Progress}" />
56	</StackLayout>
57	</ContentPage>
58
59	<!-- ❌ Wrong: x:DataType scattered on children -->
60	<ContentPage x:DataType="vm:MainViewModel">
61	<StackLayout>
62	<Label Text="{Binding Title}" />
63	<Slider x:DataType="x:Object" Value="{Binding Progress}" />
64	</StackLayout>
65	</ContentPage>
66	```
67
68	### DataTemplate always needs its own x:DataType
69
70	```xml
71	<CollectionView ItemsSource="{Binding People}">
72	<CollectionView.ItemTemplate>
73	<DataTemplate x:DataType="model:Person">
74	<Label Text="{Binding FullName}" />
75	</DataTemplate>
76	</CollectionView.ItemTemplate>
77	</CollectionView>
78	```
79
80	### Enforce binding warnings as errors
81
82	\| Warning \| Meaning \|
83	\|---------\|---------\|
84	\| XC0022 \| Binding path not found on the declared `x:DataType` \|
85	\| XC0023 \| Property is not bindable \|
86	\| XC0024 \| `x:DataType` type not found \|
87	\| XC0025 \| Binding used without `x:DataType` (non-compiled fallback) \|
88
89	Add to the `.csproj`:
90
91	```xml
92	<WarningsAsErrors>XC0022;XC0025</WarningsAsErrors>
93	```
94
95	---
96
97	## Binding Modes
98
99	Set `Mode` explicitly only when overriding the default. Most properties
100	already have the correct default:
101
102	\| Mode \| Direction \| Use case \|
103	\|------\|-----------\|----------\|
104	\| `OneWay` \| Source → Target \| Display-only (default for most properties) \|
105	\| `TwoWay` \| Source ↔ Target \| Editable controls (`Entry.Text`, `Switch.IsToggled`) \|
106	\| `OneWayToSource` \| Target → Source \| Read user input without pushing back to UI \|
107	\| `OneTime` \| Source → Target (once) \| Static values; no change-tracking overhead \|
108
109	```xml
110	<!-- ✅ Defaults — omit Mode -->
111	<Label Text="{Binding Score}" />
112	<Entry Text="{Binding UserName}" />
113	<Switch IsToggled="{Binding DarkMode}" />
114
115	<!-- ✅ Override only when needed -->
116	<Label Text="{Binding Title, Mode=OneTime}" />
117	<Entry Text="{Binding SearchQuery, Mode=OneWayToSource}" />
118
119	<!-- ❌ Redundan

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Type