How do I get the value from an anonymous expression?

For sake of simplicity, imagine the following code:

I want to create a Foo:

public class Foo
{
    public string Bar { get; set; }
}

And pass it to a special Html Helper method:

Html.SomeFunction(f => f.Bar);

Which is defined as:

public string SomeFunction<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression)

I want to get the value of Bar inside of this function, but have absolutely no idea how to get it.