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<img src="/package_icon.png" height="30px"> PropertyChanged.Fody

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Injects code which raises the PropertyChanged event, into property setters of classes which implement INotifyPropertyChanged.

See Milestones for release notes.

This is an add-in for Fody

It is expected that all developers using Fody become a Patron on OpenCollective. See Licensing/Patron FAQ for more information.

Usage

See also Fody usage.

NuGet installation

Install the PropertyChanged.Fody NuGet package and update the Fody NuGet package:

PM> Install-Package Fody
PM> Install-Package PropertyChanged.Fody

The Install-Package Fody is required since NuGet always defaults to the oldest, and most buggy, version of any dependency.

Add to FodyWeavers.xml

Add <PropertyChanged/> to FodyWeavers.xml

<Weavers>
  <PropertyChanged/>
</Weavers>

Overview

NOTE: All classes that implement INotifyPropertyChanged will have notification code injected into property setters.

Before code:

public class Person : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    
    public string GivenNames { get; set; }
    public string FamilyName { get; set; }
    public string FullName => $"{GivenNames} {FamilyName}";
}

What gets compiled:

public class Person : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    string givenNames;
    public string GivenNames
    {
        get => givenNames;
        set
        {
            if (value != givenNames)
            {
                givenNames = value;
                OnPropertyChanged(InternalEventArgsCache.GivenNames);
                OnPropertyChanged(InternalEventArgsCache.FullName);
            }
        }
    }

    string familyName;
    public string FamilyName
    {
        get => familyName;
        set 
        {
            if (value != familyName)
            {
                familyName = value;
                OnPropertyChanged(InternalEventArgsCache.FamilyName);
                OnPropertyChanged(InternalEventArgsCache.FullName);
            }
        }
    }

    public string FullName => $"{GivenNames} {FamilyName}";

    protected void OnPropertyChanged(PropertyChangedEventArgs eventArgs)
    {
        PropertyChanged?.Invoke(this, eventArgs);
    }
}

internal static class InternalEventArgsCache
{
    internal static PropertyChangedEventArgs FamilyName = new PropertyChangedEventArgs("FamilyName");
    internal static PropertyChangedEventArgs FullName = new PropertyChangedEventArgs("FullName");
    internal static PropertyChangedEventArgs GivenNames = new PropertyChangedEventArgs("GivenNames");
}

(the actual injected type and method names are different)

Code Generator

Starting with version 4 PropertyChanged.Fody ships with a C# code generator that can even more simplify your code by generating the boilerplate of the basic INotifyPropertyChanged implementation for you directly as source code.

Simply mark a class implementing INotifyPropertyChanged or having the [AddINotifyPropertyChangedInterface] attribute as partial and the generator will add the necessary event and event-invokers:

e.g. a class like this:

public partial class Class1 : INotifyPropertyChanged
{
    public int Property1 { get; set; }
    public int Property2 { get; set; }
}

will be complemented by the generator with this:

public partial class Class1
{
    public event PropertyChangedEventHandler? PropertyChanged;
    protected void OnPropertyChanged([CallerMemberName] string? propertyName = null)
    {
        OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
    }
    protected virtual void OnPropertyChanged(PropertyChangedEventArgs eventArgs)
    {
        PropertyChanged?.Invoke(this, eventArgs);
    }
}

Code Generator Configuration

You can configure the code generator via properties in your project file:

<PropertyGroup>
  <PropertyChangedAnalyzerConfiguration>
    <IsCodeGeneratorDisabled>false</IsCodeGeneratorDisabled>
    <EventInvokerName>OnPropertyChanged</EventInvokerName>
  </PropertyChangedAnalyzerConfiguration>
</PropertyGroup>

Workaround for WPF projects targeting multiple frameworks:

WPF projects targeting multiple frameworks may fail during the compilation of the *_wpftmp.csproj with

... error CS0111: Type 'SomeType' already defines a member called 'OnPropertyChanged' with the same parameter types

This can be fixed by adding this build target to your project:

<Target Name="RemoveDuplicateAnalyzers" BeforeTargets="CoreCompile">
  <!-- see https://github.com/dotnet/wpf/pull/6680 -->
  <RemoveDuplicates Inputs="@(Analyzer)">
    <Output
      TaskParameter="Filtered"
      ItemName="FilteredAnalyzer"/>
  </RemoveDuplicates>
  <ItemGroup>
    <Analyzer Remove="@(Analyzer)" />
    <Analyzer Include="@(FilteredAnalyzer)" />
  </ItemGroup>
</Target>

Notes

For more information, see the wiki pages.

Icon

Icon courtesy of The Noun Project