C#

Autofac: resolve dependencies later in code & pass your parameters

March 22, 2012 .NET, Autofac, C#, IoC 3 comments

Today I played a bit with Autofac, and I learned few simple but nice tricks. This blog post is for my personal notes. If you haven’t used Autofac or know little about IoC it might be of interest for you.
Below we have fun setup. I call it “fun”, because it is very explicit and easy to understand. Reading though it makes it clear what dependencies are:
builder
    .Register(b => new F())
    .As<IF>();

builder
    .Register(b => new E())
    .As<IE>();

builder
    .Register(b => new D1())
    .Named<ID>(SomeD1Name);

builder
    .Register(b => new D2())
    .Named<ID>(SomeD2Name);

builder
    .Register((b,prms) => new C(b.Resolve<IE>(), prms.TypedAs<IF>()))
    .Named<IC>(CName);

builder
    .Register((b,prms) => new B(b.Resolve<IF>(), b.ResolveNamed<IC>(CName, prms)))
    .As<IB>();

builder
    .Register(b => new A(b.Resolve<IE>(), 
        b.ResolveNamed<ID>(SomeD1Name),
        b.ResolveNamed<ID>(SomeD2Name)))
    .As<IA>(AName);

builder
    .Register(b => new Service(b.Resolve<IComponentContext>(),
        b.Resolve<IA>(), b.Resolve<IB>()))
    .As<IService>();

And that’s it.

I would like to pay your attention to few things. One of them is “prms.TypedAs”, which is great way to inject parameters for your construction later on. Another thing is passing IComponentContext to the Service instance. This two things altogether will allow you to resolve dependencies inside of your Service class, just like below (assuming you have field _componentContext):
_componentContext.Resolve<IB>(new TypedParameter(typeof(IF), new F1()));

As you understood this will create us instance of B, by passing into its constructor instance of F and instance of C, created basing on E and another implementation of IF, which is F1 (not one registered at very beginning). Isn’t it nice?
For serious reading on Autofac please refer to its web site:


3 comments


Working with FTP for the first time? Quick setup & quick C# code.

March 21, 2012 .NET, C#, QuickTip No comments

Recently I had some FTP work to do. Nothing special, but in case you need quick guide on setting up FTP and writing access code in .NET you might find this interesting. Also you know where to find it in case you need it later.

I will define simple task and we will solve it!

Task:

Imagine we have external FTP server, where some vendor puts many files. Of course they provided us with credentials. We want to connect to server and then parse some files from the whole list of files. Also for testing purposes we are going to mock external service with our own local.

Setup FTP:

1) Enable FPT in Windows features.

image

2) Go to IIS –> Sites –> “Add FPT Site…”. You would need to specify some folder.

3) As for our task we want to mock some system. Following setup might be good:

  • Binding with all assigned host names and port 21
  • No SSL
  • Allow for Anonymous and Basic Authentication
  • Add Read permissions for All Users and Anonymous

You should see something like this:

image

image

You will be able to access FTP locally without any issues and need to provide credentials.

4) Go to User Accounts –> Advanced –> Advanced –> New User… Create user you would like use when connecting to FTP.

image

5) Go to IIS -> your FTP site –> Basic Settings –> Connect as… –> Specific User. And enter same user again.

image

We added this user because we need to imitate situation in which our code and FTP have different credentials.

Access code:

To get list of files on server (using WebRequest):

public List<string> FetchFilesList()
{
    var request = WebRequest.Create(FtpServerUri);
    request.Method = WebRequestMethods.Ftp.ListDirectory;

    request.Credentials = new NetworkCredential(UserName, UserPassword);

    using (var response = (FtpWebResponse)request.GetResponse())
    {
        var responseStream = response.GetResponseStream();

        using (var reader = new StreamReader(responseStream))
        {
            var fileNamesString = reader.ReadToEnd();
            var fileNames = fileNamesString.Split(Environment.NewLine.ToCharArray(), StringSplitOptions.RemoveEmptyEntries);

            return fileNames.ToList();
        }
    }
}

To fetch some file contents as XDocument (using WebClient):

public XDocument FetchFile(string fileName)
{
    var client = new WebClient();
    client.Credentials = new NetworkCredential(UserName, UserPassword);

    var fileUri = new Uri(FtpServerUri, fileName);
    var downloadedXml = client.DownloadString(fileUri);
    return XDocument.Parse(downloadedXml);
}

I don’t think those two chucks of code need lot of explanations. As you can see with WebClient there is less code, but this way you cannot specify request ftp method.

Hope this overview is quick and not too much noisy.

NOTE: I’m not professional administrator, so my FTP setup may be somewhatwrong, but it satisfied needs of task described in the beginning of blog post.

In any case here are some links:


No comments


Custom configuration: collection without “add” plus CDATA inside

March 20, 2012 .NET, C#, QuickTip 2 comments

This blog post might look like any other standard blog posts, answering question, which can be googled and found on stackoverflow. But it isn’t. You see… it composes couple of interesting things you might need for you custom configuration. Also it is not congested with explanations. I’m adding this as quick reference for myself, so I don’t spend my time googling a lot to find answers. Also if you just starting with custom configuration and don’t want to read MSDN pages, please refer to my earlier blog post on basics here.

Let’s get back to topic:

We want section in our app/web.config with collection which will be able to contain elements without ugly “add” tag and also have CDATA inside. See configuration:

    <Feeds defaultPollingInterval="00:10:00">
      <Feed>
        <![CDATA[http://www.andriybuday.com/getXmlFeed.aspx?someParam=A&somethingElse=B]]>
      </Feed>
      <Feed pollingInterval="00:05:00">
        <![CDATA[http://www.andriybuday.com/getXmlFeed.aspx?someParam=C&somethingElse=D]]>
      </Feed>
    </Feeds>

So as you can see in collection of elements there is custom name “Feed”, which is awesome. Also notice that URL contains weird characters (not for us, but for XML), so we surround URL into CDATA. Those feeds are fake of course.

To make all this happen we need few things:

  1. Override CollectionType property for our collection, and set type to BasicMap
  2. Override ElementName property for our collection, and return preferred name
  3. Override DeserializeElement method for element inside collection. Here you need to manually fetch your attributes, like I do for poollingInterval and read contents of CDATA. Please refer to source code below to see how this is done as it is bit tricky. For example because of the nature of the XmlReader you need to read attributes first and then proceed to contents.

Source code below (interesting pieces are in bold):

[ConfigurationCollection(typeof(FeedConfigElement))]
public class FeedsConfigElementCollection : ConfigurationElementCollection
{
    [ConfigurationProperty("defaultPollingInterval", DefaultValue = "00:10:00")]
    public string DefaultPollingInterval
    {
        get
        {
            return (string)base["defaultPollingInterval"];
        }
    }
    protected override ConfigurationElement CreateNewElement()
    {
        return new FeedConfigElement();
    }
    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((FeedConfigElement)(element)).Url;
    }

    // In order to avoid standard keyword "add"
    // we override ElementName and set CollectionType to BasicMap
    protected override string ElementName
    {
        get { return "Feed"; }
    }

    public override ConfigurationElementCollectionType CollectionType
    {
        get { return ConfigurationElementCollectionType.BasicMap; }
    }
    public FeedConfigElement this[int index]
    {
        get
        {
            return (FeedConfigElement)BaseGet(index);
        }
    }
}

public class FeedConfigElement : ConfigurationElement
{
    public string Url { get; private set; }

    public string PollingInterval { get; private set; }

    // To get value from the CDATA we need to overrride this method
    protected override void DeserializeElement(XmlReader reader, bool serializeCollectionKey)
    {
        PollingInterval = reader.GetAttribute("pollingInterval") ?? "00:00:00";

        // Also for some unknown reason for CDATA ReadElementContentAsString returns 
        // a lot of spaces before and after the actual string, so we Trim it
        Url = reader.ReadElementContentAsString().Trim();
    }
}

Hope this gives quick answers to some of you. It took me good portion of time to find all this things, because for some odd reason it wasn’t so much easy to find.

Some links:


2 comments


I gave up with Design Patterns in Java – I start my book

September 26, 2010 C#, Design Patterns, Java, Opinion, Personal, Success 12 comments

Yeah, title sounds not logically, but you will understand in a few why it is still relevant to this blog post.

It was and it is a good idea to…

In one of my blog posts I’ve decided to have all of the GoF Design Patterns written with Java. And idea itself is very good. Having all of the design patterns written by your own with you own examples gives you understanding of the DP that you cannot gain anywhere else plus to that if you have industrial experience of using all of them you can start think that you are guru of DP.

Process of writing my post on one of the Design Patterns looks like this: I read chapter of the GoF book on the particular DP, then I think up my own example if I do not have it already in my mind and after I’m done with some preliminary ideas I search over the internet for interesting articles on it and probably rethink some of the aspects of my example. After all of that I proceed to writing blog post and source code with Java.

Conclusion: Awesome and probably one of the best ways of learning DP is to have your own example of using it and industrial experience.

Design Patterns articles

One of the intents of having DP written in Java was to familiarize with that language. But it turns out that I did not learn much from Java (except of few things). Also few months ago I started keeping up Tuesday’s Design Pattern on the Lviv .NET User Group Page. Since it is .NET specific UG, I used to do following: 1) translate and 2) translate. In first place it is translation from English to Ukrainian and in second from Java to C#. When with item number one I have to apply some logic and rephrasing I cannot say the same about second item. I just copy code-paste code into Visual Studio and change few keywords. So what do I learn regarding of Java in this case?

I will continue learning Java, but I have to consider better way of doing it. I will also continue writing about Design Patterns, but with examples in C#.

Conclusion: Learning another programming language (Java) is really great idea, but be sure that you choose right approach of doing this.

First free e-book

On the road to Lviv I got perfect idea to start my first book. Of course this cannot be comprehensive stunning author’s book, but I have to start with something. In other words some probing book and this could be this “try it” case. I’m almost sure that there are no books about GoF Design Patterns in Ukrainian. (I suppose that there are in Russian, which can be easily understandable for most Ukrainians…)

How this book will be different?

  • It will be in Ukrainian.
  • It will NOT be a translation of GoF book in any way.
  • It will have my own unique examples.
  • It will be short and easy to understand.
  • It will be really cool kick-off book on DP for starting Developers.
  • It will be free to download.

Why do I need it?

I understand that this book might not be popular at all. But I have to start with something and plus to this it will help me familiarize with the whole process and build my confidence for future.

Also if you have some doubts about my idea I have a question for you: “Have you ever dreamt about your own book? If yes, do you have at least small book written?”

Conclusion: Never be skeptic about starting your first book. It might be a huge step to your success as anything else you are hesitating about but still dreaming about it!


12 comments


.NET Remoting Quickly

August 11, 2010 .NET, C#, HowTo No comments

As you may know recently I got junior to mentor him. In order to understand his capabilities and knowledge I asked him to do couple of things, like explain me one Design Pattern he knows, explain SCRUM and write the simplest .NET Remoting. So that was yesterday and today I verified that he failed with .NET Remoting, but it doesn’t mean that he is bad. He just need learn googling art more. I asked that for next day, and gave him stored procedure to write. Hope he will be smart enough to finish it till I come tomorrow from my English classes.

.NET Remoting

To ensure that I’m not asshole that asks people to do what I cannot do, I decided to write it by my own and see how long will it take for me. It took me 23 minutes. Hm… too much, but I should complain at VS about “Add Reference” dialog.

So here we have three projects in Visual Studio: one for Server, one for Client and of course Proxy class shared between client and server.

Shared proxy class ChatSender in ChatProxy assembly:

    public class ChatSender : MarshalByRefObject
    {
        public void SendMessage(string sender, string message)
        {
            Console.WriteLine(string.Format(“{0}: {1}”, sender, message));
        }
    }

Server (ChatServer):

    class Program
    {
        static void Main(string[] args)
        {
            var channel = new TcpServerChannel(7777);
            ChannelServices.RegisterChannel(channel, true);
            RemotingConfiguration.RegisterWellKnownServiceType(typeof(ChatSender),
                “ChatSender”, WellKnownObjectMode.Singleton );
            Console.WriteLine(“Server is started… Press ENTER to exit”);
            Console.ReadLine();
        }
    }

Client (ChatClient assembly):

    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(“Client is started…”);
            ChannelServices.RegisterChannel(new TcpClientChannel(), true);
            var chatSender =
                (ChatSender)Activator.GetObject(typeof(ChatSender), “tcp://localhost:7777/ChatSender”);
            string message;
            while ((message = Console.ReadLine()) != string.Empty)
            {
                chatSender.SendMessage(“Andriy”, message);   
            }
        }
    }

My results


No comments


Threading.Timer vs. Timers.Timer

June 9, 2010 .NET, C#, Concurrency, Performance 5 comments

I agree that title doesn’t promise a lot of interesting stuff at first glance especially for experienced .net developers. But unless you encounter some issue due to incorrect usage of timers you will never think that root is in timers.

System.Threading.Timer vs. System.Windows.Forms.Timer

In few words what are differences between Threading and Forms timers just to start with something.
System.Threading.Timer executes some method on periodic bases. But what is interesting is that execution of method is performed in separate thread taken from ThreadPool. In other words it calls QueueUserWorkItem somewhere internally for your method at specified intervals.
System.Windows.Forms.Timer ensure as that execution of our method will be in the same thread where we’ve created timer.

What if operation takes longer than period?

Let’s now think what will happen if the operation we set for execution takes longer than interval.

When I have following code:

    internal class LearningThreadingTimer
    {
        private System.Threading.Timer timer;
        public void Run()
        {
            timer = new Timer(SomeOperation, null, 0, 1000);
        }
        private void SomeOperation(object state)
        {
            Thread.Sleep(500);
            Console.WriteLine(“a”);
        }
    }

my application behaves well – prints “a” twice a second. I took a look for number of threads in Task Manager and it stays constantly (7 threads).
Let now change following line: Thread.Sleep(500) to Thread.Sleep(8000). What will happen now? Just think before continue to read.
I’m almost completely sure that you predicted printing “a” every second after 8 seconds have passed. As you already guessed each of the “a” printings are scheduled in separate threads allocated from ThreadPool. So… amount of threads is constantly increasing… (Every 1.125 seconds :) )

Issue I’ve been investigating

Some mister X also figured out that Console.WriteLine(“a”) is critical and should run in one thread, at least because he is not sure how much does it take to execute Thread.Sleep(500). To ensure it will run in one thread he decided to have lock, like in code below:

    internal class LearningThreadingTimer
    {
        private System.Threading.Timer timer;
        private object locker = new object();
        public void Run()
        {
            timer = new Timer(SomeOperation, null, 0, 1000);
        }
        private void SomeOperation(object state)
        {
            lock (locker)
            {
                Thread.Sleep(8000);
                Console.WriteLine(“a”);   
            }
        }
    }

Yes, this code ensures that section under lock is executed in one thread. And you know this code works well unless your execution takes few hours and you will be out of threads and out of memory. :) So that is an issue I’ve been investigating.

My first idea was System.Windows.Forms.Timer

My first idea was to change this timer to the System.Windows.Forms.Timer, and it worked well in application, but that application is able to run in GUI and WinService modes. But there are so many complains over interned to do not use Forms.Timer for non UI stuff. Also if you put Forms.Timer into your console application it will simply not work.

Why System.Timers.Timer is good toy?

System.Timers.Timer is just wrapper over System.Threading.Timer, but what is very interesting is that it provides us with more developer-friendly abilities like enabling and disabling it.

My final decision which fixes issue is to disable timer when we are diving into our operation and enable on exit. In my app timer executes every 30 seconds so this could not be a problem. Fix looks like:

    internal class LearningTimersTimer
    {
        private System.Timers.Timer timer;
        private object locker = new object();
        public void Run()
        {
            timer = new System.Timers.Timer();
            timer.Interval = 1000;
            timer.Elapsed += SomeOperation;
            timer.Start();
        }
        public void SomeOperation(object sender, EventArgs e)
        {
            timer.Enabled = false;
            lock (locker)
            {
                Thread.Sleep(8000);
                Console.WriteLine(“a”);
            }
            timer.Enabled = true;
        }
    }

And it looks that we don’t need lock there, but I left it there just to be sure is case if SomeOperation will be called from dozen of other threads.

MAKE DECISION ON TIMER BASING ON THIS TABLE (from msdn article)

System.Windows.Forms System.Timers System.Threading
Timer event runs on what thread? UI thread UI or worker thread Worker thread
Instances are thread safe? No Yes No
Familiar/intuitive object model? Yes Yes No
Requires Windows Forms? Yes No No
Metronome-quality beat? No Yes* Yes*
Timer event supports state object? No No Yes
Initial timer event can be scheduled? No No Yes
Class supports inheritance? Yes Yes No
* Depending on the availability of system resources (for example, worker threads

I hope my story is useful and when you will be searching like “C# Timer Threads issues” or “Allocation of threads when using timer” you will find my article and it will help you.


5 comments


Moving C# code to Java

May 9, 2010 C#, Java, MasterDiploma, Opinion 4 comments

Is CLR worse than JVM or it is just because my code is bad?

Today I had conversation with one man, who is great defender and evangelist of Java related technologies.

We talked about some algorithm implemented by me with C#. That is implementation of SOM algorithm and Concurrency stuff for it. My concurrency implementation doesn’t show time improvements unless grid size is big. He was able to achive better result with small grid sizes.

There could mean two reasons:

  • CLR concurrency model gives up in front of JVM concurrency
  • My implementation has gaps… which is more likely :)

Taking into consideration that I’m getting better results when grid is of bigger sizes I could suppose that in my algorithm there is code which takes constant (or near that) time and is not paralleled.

When I look at picture of Task Manager when my programm is executing I see that second processor has  gaps when it does nothing:

This could mean only one: I need to take better look what else is executed in one thread in my application and could be paralleled.

Converting C# code to Java

But back to that man and Java. I said to myself that it is possible to move my code to Java if something.

C# to Java Converter

Download C# to Java Converter demo version from here. Since it is demo you could not convert more than 1000 lines of your code. Order costs 119$.
Because of that I was forced to remove all not necessary code. I removed all concrete classes that I’m not using and GUI, but that did not help. I did not know how much should I delete more.

Number of lines in my project/solution

I googled for line numbers in C# and found this nice tool:

Now I know that my program has about 4000 lines of code. I left about 980 lines of code in two projects that I needed and was porting them to Java separately.

Converter GUI

And converted them to Java:

Is conversion an easy task?

Conversion could be painful if you have a lot of code that interacts with system, like threads, reading and writing to files, reading configuration file, etc.

Also it was not able to recognize ‘var’ keyword. It shows me this:

//C#
TO JAVA CONVERTER TODO TASK: There is no equivalent to implicit typing
in Java:

var neuronsCount =
getNetwork().getNeurons().size();

I moved back to my C# code and changed all var to the explicit types. And regenerated Java code.

There were some troubles when I’m delivering from List<T> and doing some stuff around that.
This code:

                int a =
this[next];
                this[next] = this[i];
                this[i] = a;

I rewrote manually to:

                int a =
super.get(next);
                super.set(next, super.get(i));
                super.set(i, a);

Also Converter was not able to convert this:

Console.ReadKey();

The biggest challenge is ThreadPool and synchronizing threads tech-nicks. This requires lot of google search that shows me that instead of ManualResetEvent I could use CyclicBarrier and how to utilize thread queuing in Java.

P/S I need to find gaps in my code to show that at least CLR and myself are not so much bad things in this world :)


4 comments