I was wondering if we should get the warning icon image only if the package source is HTTP. It is possible that I don't understand the whole context of how it works currently because I don't know much about WinForms or WPF.

Another option is to get the image only once and use it as and when needed.

I'd go further and say we should store the image in a static variable. This method, OnDrawItem, is called once per package source. There's no need to 1. get the image service instance since Visual Studio services are singletons, and 2. get the known image, which I'm reasonable confident is also a singleton. Admittedly customers don't open the dialog box very often, but this is an easy perf improvement, and this is happening on the UI thread after all.

I'd go further and say we should store the image in a static variable. This method, OnDrawItem, is called once per package source. There's no need to 1. get the image service instance since Visual Studio services are singletons, and 2. get the known image, which I'm reasonable confident is also a singleton. Admittedly customers don't open the dialog box very often, but this is an easy perf improvement, and this is happening on the UI thread after all.

Properties are just methods with some syntactic sugar, and static methods are just methods that don't have a this "variable". In order to use a static for caching, it must be a static field.

Also, some people (myself included) believe that properties should not have "business logic", although I don't think this is in our team coding guidelines. It's much easier to understand and optimize for both correctness and performance when we can assume that fields and properties will return values already in memory (and don't change state), and methods are called when internal state is changed or when potentially expensive calculations need to be made.

So, I suggest removing these two static properties, add a private static Icon _warningIcon;, and a private Icon GetWarningIcon() that returns _warningIcon when it's not null, and gets the icon from the image service when it is null.

This needs to be in a string resource, so it can be localized for the customer's language.