how to get knowing more about a class behaviour without looking at its manual?(a fundamental question about how to dive more into OOP) - oop

Question

I'm practicing OOP for 2 years (for real) and I know how to consume objects and packages and I'm developing stuffs mostly using C# .
but I have a problem with consuming unknown objects and packages as an instance :
for now I am working on an enterprise like website and for part of our job we need to consume RSS. I decided to use "System.Xml.Xpath"
and my real problem is:
for using system.xml.xpath I should look at manual and read it carefully and I don't want to do that every time.A plain example of that is like following code :
XPathDocument xp = new XPathDocument(sites[2]);
XPathNavigator nav = xp.CreateNavigator();
XPathNodeIterator it = nav.Select(xpath3);
foreach (XPathNavigator n in it)
{
//get elements here
}
//another way of iterating elements is
while(it.movenext())
{
//it.current.Value;
}
for the "foreeach" part I got it from MSDN manual and I guess I could get this simple fact by looking at class structure.
but I don't know which structure I should look.
I know how to read tooltips and I'm familiar with things like : [] / collection / enum /generic / Ienumerable / Idisposable etc...
but I think there is something about reading class behaviors and I'm missing that part.
for make it more lucid :
I know whenever we have a class that inherited from IEnumerable so we can use foreach statement against that class to iterate it through
my real problem is I think classes are self described enough to not to look at manuals all the time but I don't know how/where to read those descriptions of classes so I need your advice to get more familiar with how to reading classes without looking at manuals.
best regards.

Answer 1

Classes can (and should) be documented with source code comments, and in many languages you can generate API documentation from these comments (in HTML, XML or other format). In Java it is called Javadoc; I don't know the C# term. If this is what you call "manual", then this is your primary source of information. Other than reading the source code comments and the code itself (which you often don't have access to, especially in the MS universe). If you don't find enough information in the API documentation, you can always try googling for more explanation, tutorials or usage examples.
Hope this helps; I am not entirely sure I understood your question though. If this is not the answer you are looking for, please clarify.