C#•3mo ago

Can't access interface method

I have an interface with a defined method - RegisterLanguageChange, but I can't use it in the class that implements the interface. Although I can use ChangeLanguageVersion. Why?

C#
internal interface ILanguageChanged
{
    protected void RegisterLanguageChange()
    {
        MainWindow mainWindow = (MainWindow)Application.Current.MainWindow;
        mainWindow.LanguageChanged += this.ChangeLanguageVersion;
    }

    protected void ChangeLanguageVersion(string language);
}

C#
internal interface ILanguageChanged
{
    protected void RegisterLanguageChange()
    {
        MainWindow mainWindow = (MainWindow)Application.Current.MainWindow;
        mainWindow.LanguageChanged += this.ChangeLanguageVersion;
    }

    protected void ChangeLanguageVersion(string language);
}

3 Replies

Sossenbinder•3mo ago

The main problem (aside from the visibilitiy) in your case is that you are using default interface implementations, which behave a bit different You'd have to cast this to the actual interface

Sossenbinder•3mo ago

Check out https://andrewlock.net/understanding-default-interface-methods/#default-interface-methods-are-not-inherited for an explanation

Andrew Lock | .NET Escapades

Understanding C# 8 default interface methods

In this post I provide an introduction to default interface methods, how they work at a high level, their typical uses, and some of their sharp edges

Angius•3mo ago

Ideally, avoid implementation in interfaces. It was added as a tool to help with refactoring more than anything else, and should not be reached for as the default solution.

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Can't access interface method