README.md

NotifyValueChanged - Automatic Event Firing on Property Value Changes

A source generated approach, to turn your backing fields into properties that can fire events when their value changes - Automagically!

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Installation

Install via Nuget Install-Package TomLonghurst.Events.NotifyValueChanged

Usage

• Make your class partial
• Declare a private field - This is the backing field for which the property will be generated for.
• Add the [NotifyValueChange] attribute to the field
• That's it!

public partial class Person
{
    [NotifyValueChange]
    private string _name;
}

Your class now has a property called Name - And you can subscribe to an event called OnNameValueChange that will fire whenever the value of Name changes.

You can do this for multiple fields, and each one should generate you a separate event that you can subscribe to called On{PropertyName}ValueChange

var person = new Person();

person.OnNameValueChange += (sender, eventArgs) =>
{
    Console.WriteLine($"Name was: '{eventArgs.PreviousValue}' and is now '{eventArgs.NewValue}'\n");
};

person.Name = "Tom"; // Event will fire and log to the console "Name was: '' and is now 'Tom'"
person.Name = "Tom"; // No event will fire because the value hasn't changed
person.Name = ""; // Event will fire and log to the console "Name was: 'Tom' and is now ''"

If your class implements an interface and you want this event to be exposed on the interface, then:

• Make your interface partial
• Declare the property on the interface as normal
• Add the attribute [GenerateInterfaceValueChangeEvent]

public partial interface IPerson
{
    [GenerateInterfaceValueChangeEvent]
    private string Name { get; }
}