C# Parital Methods

Update: Orcas Beta 2 is out, and I found a problem in my syntax. Now fixed.

I was just looking through the Orcas Beta 1, and I saw something I have been waiting to talk about...Partial Methods!

This allows you to create a method sub in a partial class so you can provide the implementation in another partial class.

A case where I would use this: in code generation. You generate a data object as a partial class. Now say you want to customize the constructor a bit more. Current you have to use inheritance to do that -- but then you have to remember to use the inherited class and not the generated calss. But with partial methods you can use the main class and provide that logic. Also, if the partial method is not implemented in the other partial class, it is taken out by the compiler. Nice.

A second use: logging. You can stub out methods where you would like logging to occur, but you don't want the partial class to have to deal with the implementation of logging, making it easier to switch out later.

I hope you see why I am excited about this enhancement.

A couple of caveats though,

1. the method must return void (or a sub for you VB folks).
2. out parameters are not allowed -- but parameters are allowed in general.
3. You are not allowed access to internal/private members
4. They can only be defined and implemented in a partial class.
   

Below is a stub implementation:

// my generated class in file1.cs
public partial class Class1
{
// a partial method
partial void CalledByInit();

public void Init()
{
CalledByInit();
}

}

// my implementation class in file2.cs
public partial class Class1
{
public void CalledByInit()
{
// do my stuff here
}
}

Now why is this better than:
1. just declaring a delegate in the middle of your class?
2. passing in the code as a predicate parameter?

The answer:
1. A delegate can be assigned by anyone, and potentially have multiple implementations. That isn't always good. The partial method can only have one implementation and only by other partial class.
2. aesthetically that makes a really ugly call, plus it requires that the caller have intimate knowledge of the workings of the method that it shouldn't have to have. Now you can localize that knowledge in one place.

Again, thing about the main use case for the partial method: it should be used in conjunction with code generators. If any of you have used SubSonic, Typed Datasets, NHibernate, or other technologies, right now you are using a mixture of inheritance and partial classes. With this you might be able to drop the inherited class all together. And frankly, I'm for anything that reduces the number of classes lying around a project.

If you are interested in other new features in C# 3.0 I found a nice Power Point from Raj that you can check out.

Partial Methods are mentioned on LukeH's blog.
And they are talked about on the VB Team blog.

Some days your better off going home

Yesterday I spent 4 hours trying to solve an "Ambiguous match found" error in one of my ASP.NET applications that I had just converted from a Web Site to a Web Application

For any who don't know the difference, ASP.NET Web Site lets IIS compile the code as needed, but not until then. Makes debugging a nightmare and you have to deploy all of your C# code to the server. Web Applications compile to a dll and you only have to deploy the aspx and dll files.

Anyway, I spent 4 hours beating my head against this problem. I found MANY hits on google, none really helped. Including an often quoted article by Eran Sandler.

Finally I went home. I had to drive 200 miles to pick up my kids from grandma anyway yesterday night (that is round trip mileage). Four hours in a car either by yourself or with sleepy kids does give you time to think tho. I devised a plan.

My problem was confined to one custom control, I had already figured that part out. I would recreate the control piece by piece until I found the problem (don't ask why I didn't think of this earlier).

Next day, nice and fresh, I did just that. I had the problem fixed in 15 minutes. On this particular control I had a Validator control and an event with the same name. That was causing the problem (it wasn't a problem in the ASP.NET Web Site mind you -- just in the Web application).

15 minutes. That was it. About the same amount of time it took me to write this up!

Just goes to prove, when you are really beating your head against the wall over and over again, sometimes it is just better to go home.

3 months, 3 LINQ presentations

That is right, in the past 3 months I have given the same basic presentation three times. I don't know if that counts as a groove or a rut. But there are some nice things about doing that: don't need new Power Point for one. But more importantly: more questions that make you question things more.

Starting off, I'm no LINQ expert. Yet I have to distill it to the group. Luckily LINQ is an easy sell. There is something there for everyone in LINQ. But when it gets right down to it, what is LINQ about? I put it like this: FOR loops are evil and LINQ is the cure.

FOR loops are not run for cover and grab a Bible evil, more of a general GOTO type evil. It isn't as if GOTO is evil in itself, in some languages the GOTO is a required statement. But like all inherently benign language constructs, in the wrong hands it can go really badly.

For myself, I've seen some of the worst code in my life nestled in for loops. And even worse, most people don't even know it. How would they? You could say that they just don't know any better. But in reality, there often isn't a better way.

What is the FOR loop but a structured GOTO. Really, that is it. And it isn't a very thick abstraction. If you don't believe me, go check out assembly language. Same with WHILE.

Next, what are you doing in the FOR loop (looping through a list -- DUH)? Sorry, I need a better question: what are you trying to accomplish with the loop? Now, look at the loop, and how easy is it to figure that out after the fact?

There is a reason people don't like assembly anymore, it is too hard to understand after the fact AND it is to hard to write in the first place. There are too many moving parts. Even adding two number (registers) is a multi-step operation. Things you do in loops have many of the same qualities.

Here is an example: find the largest value in an array of integers.

First the array:
int[] i = int[]{1, 2, 3, 4, 5, 6, 7 };

Here is what you write in C#:

int iMax = i[0];
foreach(int j in i)
{
if (iMax < j)
iMax = j;
}

Here is what you would write thanks to LINQ (and Extension Methods):

int iMax = i.Max();

How many ways are there for the first code to go wrong? There are 6 lines, 4 of them have code. There is one obvious bug in the code anyway...what if the list has no items? You will get an index out of bounds error right there. But there are many ways to incorrectly write this code. This is also a simplistic example, so imagine how bad this can get when doing real code.

In the second example: I can't find one. Plus, there is very little chance that you, or someone else, will not understand what the code is doing.

Now this is simplistic, which is bad because it hides the true power that is hiding underneath. There is more to link than grab bag of small statistic functions (e.g. Sum, Min, Max, Count). Add in a complex object and the Where method and we begin to see.

Visualize a customer object. It will have properties like FirstName, LastName, Address, City, etc. This in in a CSV file that is coming from Sales and Marketing.

First part: load the CSV into your program. No problem, we have all done that from time to time. Now find me all of the people in Idaho. Crap.

Not in LINQ. If you loaded your data into a list (List list) you would write code like this:

var idahoCustomers = from c in list
where c.State = "ID"
select c;

Want that in Lambda:

var idahoCustomers = list.Where(c => c.State == "ID");

Something you should know about now, there are two ways of doing the same thing, and you should probably know both. First is LINQ. If you see "from blah blah where blah blah select blah blah" -- you are looking at LINQ. If you see a "=>" you are looking at Lambda.

Personally, I love Lambda more than LINQ. Lambda can do everything LINQ can do, plus everything else. Another way of saying that is "LINQ is a subset of Lambda."

Anyway, this post could run on and on about the wonders of LINQ and Lambda -- but there are plenty of other people doing that. Hopefully, you have already read some of that. Where I want to finish off with is a few suggestions for anyone looking to get a grip on all of this.

First, there are a lot of new things to learn these days. WPF, WF, WCF, LINQ, Lambda, etc. Is this different? Yes it is. You need to learn LINQ. Personally I will be asking interview questions based on link in the future.

Second, considering you have limited time, what should you concentrate on? My answer is Lambda and Extension Methods. The more you learn about Extension Methods the more you will be able to do with Lambda. (Warning, if you are going to learn Extension Methods, you should probably learn about Predicates as well).

And some words of warning. Watch your return value types. You will see a lot of IQueryable, IEnumerable, and other strange interfaces as return types. These will often be hidden in 'var's. Be warned, each has its own capabilities, and you should know how to convert between them.

For example. In a List object, you get the ForEach extension method. You don't get that with IEnumerable or IQueryable. But you can get there by calling ToList() on either of those object types.

Finally: measure. Grab a profiler and run with it. Just like FOR saved you from the uglyness of GOTO, LINQ saves you from the complexity of FOR. But it doesn't get you away from the costs. There will still be times when it is better to write the loop yourself. A good profiler will tell you when.



Oh, one final note: I'm using Visual Studio.NET 2008 Beta 1 like everyone else. All code samples are subject to change when Beta 2 releases this week.

Where are the DSLs?

DSL is a Domain Specific Language. It took me a couple of years to really wrap my head around what the term means. Now I have a bad understanding -- but where are the languages?

First off, in my understanding of a DSL, it might not be a proper definition. Frankly, I don't care if the language is a full on language, with it's own syntax and control structures, or just a set of very specific libraries that add classes and methods for easily reading what is going on inside of an existing language -- like C# or VB.NET.

Personally, I like the second one. I would take the inspiration from SubSonic and NHiberate. Heck, throw in NUnit if you want. The nice thing about using these as your examples is that you know things are easily extendable.

There are a couple that I am thinking of right now. I've been playing around with MSBuild and NANT lately. Those two tools have convinced me that XML sucks as a language format. How do you define a loop in XML? You can't do it in any terse format I can tell you that. XML is for data, not logic. That is why JavaScript doesn't look like HTML.

So no, I dont buy XML as a language. Personally, I have a hard time seeing through all of the angle bracket -- really, I do. They just seem to create a lot of unnecessary noise to me. Readability stinks, which hurts the overall expressiveness of the language -- not to mention aesthetics -- and maintainability is also terrible. Not a whole lot of syntax highlighters for xml these days. Debuggability: None. (is debuggability a word?) Either it works or it doesn't. If it doesn't...may the force be with you.

Anyway, back to the build scripts example. Basically, even if you have sample build scripts to work off of, it will easily waist one day of a developer's life to get a build script off the ground. Just to get started. Then countless more hours keeping the stupid thing up to date.

Why don't we have a build script DSL? Some already do exist, Ruby Rake is one. I'm considering learning it. I would like a C# based one, but I'll take Ruby if I have to.

Another use that I have thought of often has to do with ETL. Now I find I'm not alone. Ayande has recently been bitten by the bug. Which is good. Because with his given track record he might just be able to do it. Would you rather deal with Integration Services GUI or a language specifically designed for that purpose.

Bear in mind, these examples break down at one crucial point: threading. Both of the examples mentioned, ETL and Build Scripts, can benefit heavily from working in parallel. And that is one area that our current languages don't help us with a whole lot yet. It is easy to tell Integration Services to load a bunch of tables at the same time in the GUI -- that is a lot more work in C#.

Now it can all be mocked with the Unit of Work pattern so everything can be batched together. That would hide the complexity from the user of the language at the very least. But that still leaves a lot of complexity behind the scenes.

Which leads me to one of the new great hopes coming from Microsoft sometime in the future: PLINQ. Aka: Parallel LINQ. LINQ is all about building a better FOR loop. But it is still iterating over a list one item at a time. PLINQ takes things that next crucial step: multi-threading the iteration. And all without changing the syntax of LINQ. Now that is flippen cool. Unfortunately, I have heard no release date for PLINQ, and it probably wont come out with .NET 3.5 at all.

Anyway, those are my thoughts. I could go on, but I need to get back to work.

I (hart) Fiddler

I fell in love with Fiddler today. I was trying to duplicate a SOAP call from one client to my own. Both applications were using the same api to perform the SOAP calls, but one worked, and the other did not (mine was the one that didn't work).

Enter Fiddler. I was able to intercept the call, check what was being sent and returned, and with the help of the file compare in Context I was able to figure out the problem.

Now I've seen Fiddler before, but that was always as a that-could-be-useful-later. Today it was useful. I don't know how I would have tracked down the problem otherwise.

NetDug last week...

I thought this was funny.

Last week I gave a presentation on C# 3.0 and LINQ to NetDug. Mind you, this is a really well run group. We meet at the ProClarity ---erm Microsoft -- building in downtown Boise. Usually someone from Microsoft lets us in, guards over us, and things go really well. Not this time.

It started with one of the group leaders sending me an email, the day before the meeting, telling me that he could not get onto their server, ergo: they couldn't send an email to the group telling them that the meeting was on, and what we were talking about.

Not great, but I can work around that. I sent out a message to the BSDG group, which is also largely Boise area developers and told them. It is largely the same people anyway.

One day goes by.

OK, day of the meeting. I show up and there are already people there waiting outside the building. I'm early so I don't think much of it. The Microsoft building here in Boise is actually a nice spot. There is this cool little spot that had some places to sit in the shade with lots of trees, which was needed because it was over 80 degrees at the time. So we just sat there until someone was going to open the building for us.

Janitors walked in, a few people walked out. I even knew a few of them. It was getting really close to the time of the meeting so I started talking to one of them as they came out. Asking if certain people who are usually there to open the building for us are still in the building to open the building so we can have our meeting. (yes, that is a run on sentence, but appropriate since the person I talked to was a tech writer -- who taught tech writing). They were not there.

Great. First there is no email to tell anyone about the meeting we were supposed to have, and now we don't even have a room to have it in. This is getting better all the time.

By this time there were about eight people there. That is a small gathering for this group. It usually gets 20 people. But, they were still interested in what I had to show them. But we were outside, and my laptop is useless outside running on battery power -- so no power point. There are worse things in life than giving a talk with no power point, really. So next best option: wing it with a pen and paper.

This is where it is a good thing that there were only eight people there. So I started the meeting, outside, and started talking. One thing that does happen when giving a talk like this, you cut out all of the extraneously stuff.

Array initializers -- didn't talk about it.
Extension Methods -- yes, but just enough
Object and Collection initializers -- just barely
Expression Trees -- mentioned that I didn't know anything about them.

But we did talk quite a bit about the var keyword, anonymous types, LINQ, and Lambda. All via pen and paper (which I now refer to as the original Power Point).

So, obviously, I wasn't trying to get the attendees to really grok the material, but I think they did capture some of the general zen. Which, as far as I can tell, is to rethink how and when you use a for loop on a list. With LINQ and Lambda, we should be seeing a lot fewer of them.

In the process we also talked about PLINQ, XLINQ, DLINQ, LINQ for SQL, NHibernate, SubSonic, and Log4Net. It was a good meeting. Not bad for considering the circumstances.

Then to close off the evening for myself, my mom and brother were attending a dairy conference a few blocks away, so I snuck into there and bored myself to sleep. They were talking about whey futures (as in stock market like futures).

I thought I had given a reasonable presentation with no slides earlier, on the street, in 80 degree weather. Here was a guy giving a presentation inside, with a huge projector (20 foot screen - at least) to 50 people and doing it badly.

Now all of this comes from my own general preferences. There is an art to displaying lots of numerical data on a slide. There is also an art to showing charts on a slide. This guy knew about neither, and probably never read anything by Edward Tufte.

Note: I have read Edward Tufte, but please don't blame my bad slides on him -- they are my fault for not reading his books enough.

All of his slides were white. All of his text was black. There was no variation. They could have been printed on a black and white printer and no one would have known the difference. Imagine trying to decipher slide after slide filled with large grids of numbers, each row having a different type of number, and only a thin black line between them. Not good. Then to show emphasis on a particular number -- out comes the laser pointer.

I about made my brother buy me a beer after that. And dinner.

My mom did instead.

Fake Objects in RhinoMocks

It seems Ayende is keeping busy with Rhino Mocks (aside from blogging 5 times per day). He has now implemented Fake Objects (called a Stub in Rhino Mocks).

First to give some background, there is a difference between a Mocked object and a Fake object.
With Fake Objects, think of a simple class with only properties containing both getters and setters. You can set any property to a value, but the fake object really doesn't care what happens to it. If you set a property to a value, it returns that value until that value is set to something else. I am not sure, but I don't thing you can tell a Fake object function what to return. So if you need that, you should probably use the Mock Object -- read on.

With Mock Objects, they are much more complex beasts. You must warn the Mocked object for every call made to the object, and tell the Mocked Object what to return. One nice thing about Mocked Objects is that functions can be mocked.

Each object, Fake and Mock, has their place in a testing scheme, so it is important to know the difference. If you need simple returns with getters and setters, and don't care if something does or doesn't get called use a Fake Object. Otherwise use a Mock Object.

Anyway, if I have an interface that looks like this:

   1:  public interface IMyObject

   2:  {

   3:        public string MyProperty1 { get; set; }

   4:        public string MyProperty2 { get; set; }

   5:  }

I can create and use a Fake Object for it like this:

   1:  IMyObject o = MockRepository.GenerateStub<imyobject>();

   2:  o.MyProperty1 = "Hi";

   3:  o.MyProperty2 = "There";   

   4:  Assert.AreEqual("Hi", o.MyProperty1);

   5:  Assert.AreEqual("There", o.MyProperty2);

as apposed to creating and using a Mock Object

   1:  MockRepository mock = new MockRepository();

   2:  IMyObject o =  mock.CreateMock<IMyObject>();

   3:  Expect.Call(o.MyProperty1).Return("Hi");

   4:  Expect.Call(o.MyProperty2).Return("There");

   5:  mock.ReplayAll();

   6:  Assert.AreEqual("Hi", o.MyProperty1);

   7:  Assert.AreEqual("There", o.MyProperty1);

   8:  mock.VerifyAll();

As you can see, there is nothing special to using a Fake Object, just set and get the properties like normal. Whereas with Mock Object you have to call Expect.Call for everything that gets touched.

Have fun.

Visual Studio Shortcuts: Collapsing and Expanding text

OK, here are some shortcuts I recently rediscovered. These are in response to me suddenly finding a lot of code collapsed in Visual Studio so only the definitions were visible.

All of these shortcuts are found in the Visual Studio menu Edit->Outlining

Ctrl-M, Ctrl-M: Toggle Outlining Expansion
This one is useful if you have a single function you want to view or hide
Ctrl-M, Ctrl-L: Toggle All Outlining Expansion
Use this to view or hide an entire file
Ctrl-M, Ctrl-O: Collapse to Definitions

This is painful

There is just something painful about listening to the sound of your own voice. Almost as bad as having someone point out all of my grammatical mistakes. Then there is the added pain of watching yourself on video. You get to hear and SEE how goofy you really are.

Anyway, we recorded that last half of our BSDG meeting last Thursday where I was covering C# 3.0. The video misses all of the good stuff (like 'var', collection initializers, object initializers, extension methods, and such) and just focuses on LINQ and Lambda Expressions.

This being the web, there are far better sources of information than this video, but if you are really starved for information -- have at it.

Link to the video.

Computers and Cars

I was talking with my neighbor the other day. He was remarking on how his computer had crashed, his daughters computer had crashed, and other computer crashes. In all of these cases, the machines had been working for years with no problems -- then boom!

I asked him about his daughters computer, being the caring person I am, but she lives in another state -- but no worries, she knows a bunch of computer people who are helping her out.

Then a thought struck me (and probably not a very original one): computers are like 1960 era cars were in the 1960s. The cars back then looked good, had style, but very little in the way of safety features, and broke down from time to time. And back then, everyone knew a mechanic.

Computers today have many of the same qualities. The difference is that today, I know very few mechanics and everyone knows a computer guy or three.

Well, back in the 1960, they weren't worried about safety quite then, more on performance and reliability. And try as they might, no one really got the reliability thing down until the 1990s. That is 30 years! But for the most part, with cars today, you add gas, change the oil, and you are good to go. If something does go wrong you look up a mechanic with a computer and the car tells you what is wrong. Also, cars today are getting better gas mileage. My Suburban gets 18 MPG of all things. That is better than my old Nissan Pathfinder which was a much smaller SUV.

Granted, there is still work to be done. I do know a few mechanics and not many of them are board.

But computers are the same, we have been working on processor speed and hard-drive size that reliability has taken a back seat. Remember, 30% of backups fail to restore. But now today, we have reached our theoretical cpu performance peak, and now we are just adding more CPUs. And that can't go on for too much longer. Also, hard drives are only supposed to last for 5 years, and often last for less. But again, how much bigger can we get in our current size restrictions with our current technology.

There has to be a new push coming, if you think that history repeats itself, where reliability will be pushed. If one hard drive manufacturer could stand out and say their hard drives last for 10 years -- I know people who would buy them, lots of them.

Also is power usage. Energy isn't getting cheaper, and computers are very inefficient with power. Google has an announcement about a new power supply that would save 30% of power costs. I would buy that.

Anyway, computers are still changing rapidly, just like cars are. And trends being as they are, I suspect that will continue. Change is a given, but what is changing is not.