Given one is an expert in java will he be considered advanced in C#?

Answer 1

nope. they are not exactly the same. c# has more advanced features

Answer 2

... but on the other hand you will be fine with C#. They are not the same, as eggs are different to each other. As for advanced features in general; event handling, delegates, properties are used (differently) in C#, and also it supports more on C++ roots (like operator overloading). Many cosmetic features are (getting) supported in C#, while Java keeps being conservativ and robust. Libraries are - of course - different. But if you are familiar with Java, then C# won't be a hard challange. The concepts are nearly the same for both languages, and so the programming design as well.