# PropertyChanged
**Repository Path**: mirrors_Fody/PropertyChanged
## Basic Information
- **Project Name**: PropertyChanged
- **Description**: Injects INotifyPropertyChanged code into properties at compile time
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No
## Statistics
- **Stars**: 1
- **Forks**: 0
- **Created**: 2022-01-05
- **Last Updated**: 2026-02-15
## Categories & Tags
**Categories**: Uncategorized
**Tags**: None
## README
# 
PropertyChanged.Fody
[](https://www.nuget.org/packages/PropertyChanged.Fody/)
Injects code which raises the [`PropertyChanged` event](https://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.propertychanged.aspx), into property setters of classes which implement [INotifyPropertyChanged](https://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx).
**See [Milestones](../../milestones?state=closed) for release notes.**
## This is an add-in for [Fody](https://github.com/Fody/Home/)
**It is expected that all developers using Fody [become a Patron on OpenCollective](https://opencollective.com/fody/contribute/patron-3059). [See Licensing/Patron FAQ](https://github.com/Fody/Home/blob/master/pages/licensing-patron-faq.md) for more information.**
## Usage
See also [Fody usage](https://github.com/Fody/Home/blob/master/pages/usage.md).
### NuGet installation
Install the [PropertyChanged.Fody NuGet package](https://nuget.org/packages/PropertyChanged.Fody/) and update the [Fody NuGet package](https://nuget.org/packages/Fody/):
```powershell
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 `` to [FodyWeavers.xml](https://github.com/Fody/Home/blob/master/pages/usage.md#add-fodyweaversxml)
```xml
```
## Overview
**NOTE: All classes that implement `INotifyPropertyChanged` will have notification code injected into property setters.**
Before code:
```csharp
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:
```csharp
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:
```c#
public partial class Class1 : INotifyPropertyChanged
{
public int Property1 { get; set; }
public int Property2 { get; set; }
}
```
will be complemented by the generator with this:
```c#
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);
}
}
```
- Only classes are supported, no records.
- For nested classes, all containing classes must be partial, too.
- Code generators only work correctly in SDK-style projects
### Code Generator Configuration
You can configure the code generator via properties in your project file:
```xml
false
OnPropertyChanged
```
- *IsCodeGeneratorDisabled*: Set to `true` to switch off the code generator.
- *EventInvokerName*: Change the name of the event invoker method from `OnPropertyChanged` to your favorite name.
### 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:
```xml
```
---
## Notes
- **Dependent properties** — In the above sample, the getter for `FullName` depends on the getters for `GivenName` and `FamilyName`. Therefore, when either `GivenName` or `FamilyName` is set, `PropertyChanged` is raised for `FullName` as well. This behavior can be configured manually using the [`AlsoNotifyFor` attribute](https://github.com/Fody/PropertyChanged/wiki/Attributes#alsonotifyforattribute) on the source property, or the [`DependsOn` attribute](https://github.com/Fody/PropertyChanged/wiki/Attributes#dependsonattribute) on the target property).
- **Intercepting the notification call**
- [**Global interception**](https://github.com/Fody/PropertyChanged/wiki/NotificationInterception)
- **Class-level interception** — The `OnPropertyChanged` method will only be injected if there is no such existing method on the class; if there is such a method, then calls to that method will be injected into the setters — see [here](https://github.com/Fody/PropertyChanged/wiki/EventInvokerSelectionInjection).
- **Property-level interception** — For a given property, if there is a method of the form `OnChanged`, then that method will be called — see [here](https://github.com/Fody/PropertyChanged/wiki/On_PropertyName_Changed).
- To get the [**before / after values**](https://github.com/Fody/PropertyChanged/wiki/BeforeAfter), use the following signature for `OnPropertyChanged` / `OnChanged`:
public void OnPropertyChanged(string propertyName, object before, object after)
- To prevent a specific class from having the notification call injection, use the [`DoNotNotify` attribute](https://github.com/Fody/PropertyChanged/wiki/Attributes#donotnotifyattribute).
- To scope the rewriting only to specific classes, and not the whole Assembly, you can use the [`FilterType` attribute](https://github.com/Fody/PropertyChanged/blob/f4905b4f04335e393c8350cc5f06f02614241483/PropertyChanged.Fody/TypeNodeBuilder.cs#L18). This changes the general behavior from from opt-out to opt-in. Example: `[assembly: PropertyChanged.FilterType("My.Specific.OptIn.Namespace.")]`. The string is interpreted as a Regex, and you can use multiple filters. A class will be weaved, if *any* filter matches.
- The `INotifyPropertyChanged` interface can be automatically implemented for a specific class using the [`AddINotifyPropertyChangedInterfaceAttribute` attribute](https://github.com/Fody/PropertyChanged/wiki/Attributes#addinotifypropertychangedinterfaceattribute). **Raising an issue about "this attribute does not behave as expected" will result in a RTFM and the issue being closed.**
- for partial methods this will be done via the code generator, so the implementation is available at compile time.
- Behavior is configured via [attributes](https://github.com/Fody/PropertyChanged/wiki/Attributes), or via [options in the `Weavers.xml` file](https://github.com/Fody/PropertyChanged/wiki/Options).
For more information, see the [wiki pages](https://github.com/Fody/PropertyChanged/wiki).
## Icon
Icon courtesy of [The Noun Project](https://thenounproject.com)