{"id":27,"date":"2014-01-19T20:31:00","date_gmt":"2014-01-19T20:31:00","guid":{"rendered":"http:\/\/tpodolak.com.hostingasp.pl\/blog\/2014\/01\/19\/implementing-inotifypropertychanged-without-lambda-expressions-and-magic-strings\/"},"modified":"2016-01-30T23:40:18","modified_gmt":"2016-01-30T23:40:18","slug":"implementing-inotifypropertychanged-without-lambda-expressions-and-magic-strings","status":"publish","type":"post","link":"https:\/\/tpodolak.com\/blog\/2014\/01\/19\/implementing-inotifypropertychanged-without-lambda-expressions-and-magic-strings\/","title":{"rendered":"Implementing INotifyPropertyChanged without lambda expressions and “magic” strings"},"content":{"rendered":"

I think almost every .NET developer is familiar with INotifyPropertyChanged<\/i> interface. Typical implementation of this interface looks more or less like that:<\/p>\n

\r\npublic class NotifyPropertyBase : INotifyPropertyChanged\r\n{\r\n    public event PropertyChangedEventHandler PropertyChanged;\r\n    protected virtual void OnPropertyChanged( Expression> propertyExpression )\r\n    {\r\n        PropertyChangedEventHandler handler = PropertyChanged;\r\n        if (handler != null) handler( this, new PropertyChangedEventArgs( GetPropertyName( propertyExpression ) ) );\r\n    }\r\n\r\n    private string GetPropertyName( Expression> propertyExpression )\r\n    {\r\n        var unaryExpression = propertyExpression.Body as UnaryExpression;\r\n        var memberExpression = unaryExpression == null ? (MemberExpression)propertyExpression.Body : (MemberExpression)unaryExpression.Operand;\r\n        var propertyName = memberExpression.Member.Name;\r\n        return propertyName;\r\n    }\r\n}\r\n<\/pre>\n
Thanks to lambda expressions we can get rid of so called “magic” strings when rising PorpertyChange event.<\/p>\n
\r\nprivate int _myProperty;\r\npublic int MyProperty\r\n{\r\n    get { return _myProperty; }\r\n    set\r\n    {\r\n        if (_myProperty == value) return;\r\n        _myProperty = value;\r\n        OnPropertyChanged( ( ) => MyProperty );\r\n    }\r\n}\r\n<\/pre>\n
However, with .NET 4.5 we can even get rid of lambda expressions itself. Everything thanks to  CallerMemberNameAttribute<\/a><\/i>, which provides us information about caller of given method. Now we can rewrite NotifyPropertyBase<\/i> class as follows<\/p>\n
\r\npublic class NotifyPropertyBase : INotifyPropertyChanged\r\n{\r\n    public event PropertyChangedEventHandler PropertyChanged;\r\n    protected virtual void OnPropertyChanged( [CallerMemberName] string propertyName = null )\r\n    {\r\n        PropertyChangedEventHandler handler = PropertyChanged;\r\n        if (handler != null) handler( this, new PropertyChangedEventArgs( propertyName));\r\n    }\r\n}\r\n<\/pre>\n
From this moment we can call OnPropertyChanged<\/i> method without any arguments<\/p>\n
\r\nprivate int _myProperty;\r\npublic int MyProperty\r\n{\r\n    get { return _myProperty; }\r\n    set \r\n    {\r\n      if (_myProperty == value) return;\r\n      _myProperty = value;\r\n      OnPropertyChanged();\r\n    }\r\n}\r\n<\/pre>\n
and thanks to CallerMemberName<\/i> attribute, argument propertyName<\/i> will be filled with appropriate value.
\n\"callermembername\"<\/a>
\nSource code for this post can be found here<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
I think almost every .NET developer is familiar with INotifyPropertyChanged interface. Typical implementation of this interface looks more or less like that: public class NotifyPropertyBase : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged( Expression propertyExpression ) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) handler( this, new PropertyChangedEventArgs( GetPropertyName( propertyExpression ) […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8,3,55,42],"tags":[163,159,201,188],"class_list":["post-27","post","type-post","status-publish","format-standard","hentry","category-net-4-5","category-c","category-callermembername","category-inotifypropertychanged","tag-net-4-5","tag-c","tag-callermembername","tag-inotifypropertychanged"],"_links":{"self":[{"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/posts\/27","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/comments?post=27"}],"version-history":[{"count":4,"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/posts\/27\/revisions"}],"predecessor-version":[{"id":337,"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/posts\/27\/revisions\/337"}],"wp:attachment":[{"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/media?parent=27"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/categories?post=27"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tpodolak.com\/blog\/wp-json\/wp\/v2\/tags?post=27"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}