The method parameter needs to be a Functional interface of the type of the method reference.

MyMethod(() -> "Hello, World!");

Supplier<String> supplier = () -> "Hello, World!";
MyMethod(supplier);
MyMethod(supplier::get);
MyMethod2(supplier.get());


public static void MyMethod(Supplier<String> sup) {
    System.out.println(sup.get());
}

public static void MyMethod2(String value) {
    System.out.println(value);
}

prints

Hello, World!
Hello, World!
Hello, World!
Hello, World!

To convert a Linq query to it's Lambda equivalent:

1. Download Linqpad and run your query.
2. In the results window, click on the "λ" button in the toolbar. It's right above the Results window
3. Your query will be converted to a Lambda expression equivalent!

You must assign the lambda to a different type:

// Gives you a delegate:
Func<int, int> f = x => x * 2;
// Gives you an expression tree:
Expression<Func<int, int>> g = x => x * 2;

The same goes for method arguments. However, once you've assigned such a lambda expression to a Func<> type, you can't get the expression tree back.