如何在 VisualStudio 中消除“[某些事件]从未使用过”编译器警告？

The compiler is apparently not aware that it's being used in XAML code. Try suppressing the warning in your event definition.

Also, make sure you're actually raising the event somewhere.

You can supress individual warnings.

\Program.cs(13,20): warning CS0219: The variable 'foo' is assigned but its value is never used

In this case, CS0219 is the warning regarding variables being assigned but not used. You can either use the /nowarn:0219 flag, or add the error number in the properties pane for the project (under "Build", remember to remove the leading CS). Keep in mind the supresses all warnings of this class.

This appears to be warning 67 and can thus be suppressed with:

#pragma warning disable 67

Don't forget to restore it as soon as possible (after the event declaration) with:

#pragma warning restore 67

However, I'd check again and make sure you're raising the event somewhere, not just subscribing to it. The fact that the compiler spits out 20 warnings and not 20 errors when you comment out the event is also suspicious...

There's also an interesting article about this warning and specifically how it applies to interfaces; there's a good suggestion on how to deal with "unused" events. The important parts are:

The right answer is to be explicit about what you expect from the event, which in this case, is nothing:

public event EventHandler Unimportant
{
add { }
remove { }
}

This will cleanly suppress the warning, as well as the extra compiler-generated implementation of a normal event. And as another added benefit, it prompts one to think about whether this do-nothing implementation is really the best implementation. For instance, if the event isn't so much unimportant as it is unsupported, such that clients that do rely on the functionality are likely to fail without it, it might be better to explicitly indicate the lack of support and fail fast by throwing an exception:

public event EventHandler Unsupported
{
add { throw new NotSupportedException(); }
remove { }
}

Of course, an interface that can be usefully implemented without some parts of its functionality is sometimes an indication that the interface is not optimally cohesive and should be split into separate interfaces.

If you are forced to implement an event from an interface, that your implementation doesn't need you can do the following to avoid the warning.

public event EventHandler CanExecuteChanged { add{} remove{} }

Or you can add <NoWarn>67</NoWarn> to your project

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
...
<NoWarn>67</NoWarn>
</PropertyGroup>

The second best way is imho to clearly state that the event is not supported by throwing an exception if someone tries to subscribe to it.

public event RoutedEventHandler SearchClick
{
add { throw new NotSupportedException(); }
remove { throw new NotSupportedException(); }
}

As a variant on this, you can also just leave the add and remove methods empty to silently ignore subscriptions on the event.

The best solution is to refactor the code, perhaps pull the declaration of the event to the implementor if possible.

As a last resort, you can also disable the warning like so

#pragma warning disable 67
public event RoutedEventHandler SearchClick;
#pragma warning restore 67

You can also do the following:

public event EventHandler MyEvent = delegate {}