Note: This post is part of a series and you can find the rest of the parts in the series index.

.NET has had one out of the box way to do caching in the past, System.Web.Caching. While a good system it suffered from two issues. Firstly it was not extensible, so if you wanted to cache to disk or SQL or anywhere other than memory you were out of luck and secondly it was part of ASP.NET and while you could use it in WinForms it took a bit of juggling.

The patterns & practises team saw these issues and have provided a caching application block in their Enterprise Library which has been used by everyone who did not want to re-invent the wheel. Thankfully from .NET 4 there is a caching system now included in the framework which solves those two issues above. This is known as System.Runtime.Caching.

Slow Example

To see how to use it lets start with a process which we can cache. I have a class called Demo which has a property named Times which is of type IEnumerable<DateTime>. To set the value of Times, you call the SetTimes method and that populates the property with 5 values. However there is a delay of 500ms between each adding of DateTime to the Times property, so it takes 2.5secs to run. In my Program class I have a method, PrintTimes which creates a new Demo object, calls SetTimes and then prints the value to screen. Lastly I in my Main method I call PrintTimes three times – in total it takes 7.5secs to run.

class Program
    {
        public static void Main()
        {
            PrintTimes();
            PrintTimes();
            PrintTimes();
        }

        private static void PrintTimes()
        {
            Demo demo = new Demo();            
            Stopwatch stopwatch = Stopwatch.StartNew();
            demo.SetTimes();
            foreach (DateTime time in demo.Times)
            {
                Console.WriteLine(time);
            }
            stopwatch.Stop();
            Console.WriteLine("It took {0} to print out the times", stopwatch.ElapsedMilliseconds);
        }
    }

    class Demo
    {
        public List<DateTime> Times { get; set; }

        public void SetTimes()
        {

            if (Times == null)
            {
                Times = new List<DateTime>();
                for (int counter = 0; counter < 5; counter++)
                {
                    Thread.Sleep(500);
                    Times.Add(DateTime.Now);
                }
            }

        }
    }

The output is from this example code is below. Note the times printed are constantly changing and that it takes ~2500ms to print out each set of values.

 

Cache Example

Now I change the PrintTimes method to incorporate the caching by creating an ObjectCache which I set to use the default MemoryCache instance. I can check if the cache contains an object using the .Contains method, I retrieve from the cache using the .Get method and I add to the cache using the .Add method:

private static void PrintTimes()
{
    Demo demo;

    Stopwatch stopwatch = Stopwatch.StartNew();
    
    ObjectCache cache = MemoryCache.Default;
    if (cache.Contains("demo"))
    {
        demo = (Demo)cache.Get("demo");
    }
    else
    {
        demo = new Demo();
        demo.SetTimes();
        cache.Add("demo", demo, new CacheItemPolicy());
    }

    foreach (DateTime time in demo.Times)
    {
        Console.WriteLine(time);
    }
    stopwatch.Stop();
    Console.WriteLine("It took {0} to print out the times", stopwatch.ElapsedMilliseconds);
}

This gives the output:

 

Note the time to print out for the first one is about 60ms longer but the second two is down to 0ms and also note how the values in the three sets in are the same.

CacheItemPolicy

In the above example I just use a default CacheItemPolicy, but you could do a lot more with the CacheItemPolicy:

• AbsoluteExpiration: Set a date/time when to remove the item from the cache.
• ChangeMonitors: Allows the cache to become invalid when a file or database change occurs.
• Priority: Allows you to state that the item should never be removed.
• SlidingExpiration: Allows you to set a relative time to remove the item from cache.
• UpdateCallback & RemovedCallback: Two events to get notification when an item is removed from cache. UpdateCallback is called before an item is removed and RemovedCallBack is called after an item is removed.

Things to watch out for

• .NET 4 only ships with support for memory caching out of the box, so you will need to build your own provider if you want any other cache source.
• You must add the System.Runtime.Caching.dll reference to get access to the namespace and classes.
• This is NOT part of the .NET 4 client profile, it is only in the full .NET 4 Framework. I have logged an issue with Connect to move the assembly into the client profile and if you agree with this idea, please vote on it: 558309

Note: This post is part of a series and you can find the rest of the parts in the series index.

SortedSet<T> provides a way to have a sorted list of items, which is sorted internally in a binary tree. This is different to the index  based sorting on SortedList<T, K> or SortedDictionary<T, K>. This means that inserts and edits to the tree are done with almost no perf impact and it also means we do not need to figure out the key manually. Without an index, you may ask how does it know the sort order? The answer is that the class it is using must implement IComparable so it can sort correctly:

Usage is very simple:

public static void Main()
{
    Random random = new Random();
    SortedSet<GPSPosition> gpsPositions = new SortedSet<GPSPosition>();
    for (int counter = 0; counter < 100000; counter++)
    {
        gpsPositions.Add(new GPSPosition(random.Next(-180, 181), random.Next(-180, 181)));
    }

    foreach (GPSPosition position in gpsPositions)
    {
        Console.WriteLine(position);
    }
}

Note: I am using the same GPSPosition class from part IV. This gives the following output:

ISet<T>

Under the surface SortedSet<T> implements the new ISet<T> interface, which is especially designed for collections with unique items. HashedSet<T>, which was introduced in 3.5, has also been updated to implement ISet<T>.

Note: This post is part of a series and you can find the rest of the parts in the series index.

Lazy<T> is a new class which has been added to cater for scenarios where

• you may need to create an object early.
• the creation is expensive (CPU, memory) or slow.
• you may not need the data the object provides when you do the creation of the object.

An example of this is LINQ which does not actually execute the query when you define it. Execution of the LINQ query occurs only when you ask for the data or some calculation on the data (like .Count()). It is done this way to prevent slow or expensive (memory, CPU) operations from being called if they are not needed.

Lazy<T> allows you to assign an object, but not actually create it until needed. Example of usage:

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Before assignment");
        Lazy<Slow> slow = new Lazy<Slow>();
        Console.WriteLine("After assignment");

        Thread.Sleep(1000);
        Console.WriteLine(slow);
        Console.WriteLine(slow.Value);
    }
}

class Slow
{
    public Slow()
    {
        Console.WriteLine("Start creation");
        Thread.Sleep(1000);
        Console.WriteLine("End creation");
    }
}

Which produces a result of:

See how the start creation line is only after the assignment when we actually ask for the value. Methods on the object work the same, the first time you call a method it then does the creation.

Brian Noyes will be in South Africa next week and for one night only he will be giving a free presentation on MVVM at Microsoft’s offices in Bryanston. Brian works at IDesign and is a Connected Systems MVP and is known for being one of the top Silverlight/WPF/WCF/WF experts and so if you interested in those technologies or the MVVM pattern then this is must attend!

Details:

• Date: 11 May 2010
• Time: 6:00 PM for 6:30 PM to 7:30 PM
• Address: Microsoft, 3012 William Nicol Drive, Bryanston
• Registration: http://sadev.wufoo.com/forms/sadevelopernet-event-brian-noyes/

Note: This post is part of a series and you can find the rest of the parts in the series index.

The pub/sub pattern is a simple concept, you have a provider which has data which it pushes to subscribers and .NET 4 brings in two new interfaces IObservable<T> and IObserver<T> which make implementing this pattern very easy.

To see the usage of these interfaces, I would like to use the example of a device which has a GPS sensor which every second checks it’s position and if the position of the GPS leaves a specified area we then want to notify the cops.

GPSPosition

First we need a small class which tells us where we are, i.e. it is just a data class. Some key points of this class are

• I have implemented IComparable so I can check when the boundary is exceeded.
• I’ve overridden ToString so it prints nicely.
• I have two constructors, a default and one which takes a latitude and longitude so that I can copy the values from one object to another.
• Note that my parameter is named @long – because long is a reserved keyword in C# you can append @ to use it.

class GPSPosition : IComparable<GPSPosition>
{
    public int Lat { get; set; }
    public int Long { get; set; }

    public GPSPosition() { }

    public GPSPosition(int lat, int @long)
    {
        this.Lat = lat;
        this.Long = @long;
    }

    public override string ToString()
    {
        return string.Format("Latitude = {0:N4}, Longitude = {1:N4}", Lat, Long);
    }
    
    public int CompareTo(GPSPosition other)
    {
        if (this.Lat > other.Lat)
        {
            return 1;
        }

        if (this.Lat < other.Lat)
        {
            return -1;
        }

        // latitude is the same

        if (this.Long > other.Long)
        {
            return 1;
        }

        if (this.Long < other.Long)
        {
            return -1;
        }

        // long is the same
        return 0;
    }     
}

GPSSensor

Now we need to create our fake sensor, which when asked tells us where in the world we are. Key points here are:

• It implements IObservable<T> so it is a provider of GPSPosition data. That means we needed to implement the subscribe method so other objects can tell this class to send them the data.
• We keep a list of the observers in a List<T>
• We call the observer.OnNext to send data to it.
• We call observer.OnCompleted when we are done with monitoring, which in our example is when we exceed the boundary.
• Note that in the GetPosition method we are responsible for sending data to all the observers.

class GPSSensor : IObservable<GPSPosition>
{
    List<IObserver<GPSPosition>> observers = new List<IObserver<GPSPosition>>();
    Random random = new Random();
    public GPSPosition Position { get; set; }

    private GPSPosition boundry;

    public GPSSensor()
    {
        this.Position = new GPSPosition();
        this.Position.Lat = random.Next(0, 181);
        this.Position.Lat = random.Next(0, 181);

        boundry = new GPSPosition(this.Position.Lat + 10, this.Position.Long + 10);
    }

    public void GetPosition()
    {
        GPSPosition current = new GPSPosition(this.Position.Lat, this.Position.Long);

        Position.Lat += random.Next(0, 5);
        Position.Long += random.Next(0, 5);

        if (current.CompareTo(this.Position) != 0)
        {
            foreach (IObserver<GPSPosition> observer in observers)
            {
                observer.OnNext(this.Position);
                if (current.CompareTo(boundry) > 0)
                {
                    observer.OnCompleted();
                }
            }
        }
    }


    public IDisposable Subscribe(IObserver<GPSPosition> observer)
    {
        observers.Add(observer);
        observer.OnNext(this.Position);
        return observer as IDisposable;
    }
}

Map

Our third class, Map is a subscriber of data and it handles the outputting to the screen and notification of the cops when we move past the boundary. Key notes here:

• It implements IObserver<GPSPosition> so it is a subscriber of GPS position data.
• We implement the three methods from the interface:
• OnCompleted for when we are done.
• OnError in case something goes wrong.
• OnNext for when new data is available.

class Map : IObserver<GPSPosition>
{
    private GPSPosition lastKnown;

    public bool StillTracking { get; private set; }

    public void OnCompleted()
    {
        Console.WriteLine("The device has moved beyond the boundsof our checking, notify the cops it was last seen at: {0}", lastKnown);
        StillTracking = false;
    }

    public void OnError(Exception error)
    {
        Console.WriteLine("SkyNet has taken over and shut down the GPS");
    }

    public void OnNext(GPSPosition value)
    {
        lastKnown = value;
        Console.WriteLine("At {0} we have moved to {1}", DateTime.Now, value);
        StillTracking = true;
    }
}

Main

We have created our data structure, our provider and and our subscriber - now we just need to bring them together in our main method, which is very easy:

public static void Main()
{
    GPSSensor sensor = new GPSSensor();
    Map map = new Map();
    sensor.Subscribe(map);
    do
    {
        sensor.GetPosition();
        Thread.Sleep(1000);
    } while (map.StillTracking);
}

This produces something that looks like:

Note: This post is part of a series and you can find the rest of the parts in the series index.

Enumerations are something I have posted about before because they are very useful and with .NET 4 they have had two new methods added which could have been ripped from my personal feature requests:

HasFlag

Enums can be bitwise values if the Flag attribute is set, however checking the bitwise values was ugly and very confusing for people who hadn’t seen it before. For example:

[Flags]
enum CupboardContents
{
    Nothing = 0,
    Cups = 1,
    Plates = 2,
    Cuttlery = 4,
    Food = 8,
    DeadBodies = 16,
    Everything = Nothing | Cups | Plates | Cuttlery | Food | DeadBodies
}

static void Main(string[] args)
{
    CupboardContents motherHubberbs = CupboardContents.Nothing;
    CupboardContents normal = CupboardContents.Plates | CupboardContents.Cups | CupboardContents.Cuttlery;
    CupboardContents hitman = CupboardContents.DeadBodies;
    CupboardContents bursting = CupboardContents.Everything;

    CupboardContents test = CupboardContents.Plates;

    Console.WriteLine("Does {0} contain {1} = {2}", motherHubberbs, test, (motherHubberbs & test) == test);
    Console.WriteLine("Does {0} contain {1} = {2}", normal, test, (normal & test) == test);
    Console.WriteLine("Does {0} contain {1} = {2}", hitman, test, (hitman & test) == test);
    Console.WriteLine("Does {0} contain {1} = {2}", bursting, test, (bursting & test) == test);
}

This produces

With .NET 4 we now we get a simple method to do this check, HasFlag, which takes an enum and tells you if that is set. The following code does the same as the code above:

Console.WriteLine("Does {0} contain {1} = {2}", motherHubberbs, test, motherHubberbs.HasFlag(test));
Console.WriteLine("Does {0} contain {1} = {2}", normal, test, normal.HasFlag(test));
Console.WriteLine("Does {0} contain {1} = {2}", hitman, test, hitman.HasFlag(test));
Console.WriteLine("Does {0} contain {1} = {2}", bursting, test, bursting.HasFlag(test));

TryParse

Until now the only way to get from a string to an enum has been the Parse method:

enum Colours
{
    Red,
    Green,
    Blue
}

static void Main(string[] args)
{
    Colours red = (Colours)Enum.Parse(typeof(Colours), "Red");

    Console.WriteLine(red);
}

Which produces

However get the string wrong and you were forced to deal with an ArgumentException:

With .NET 4, you now can use TryParse method and check the returned value first to see if the conversion was successful:

enum Colours
{
    Red,
    Green,
    Blue
}

static void Main(string[] args)
{
    Colours red;
    Colours purple;
    if (Enum.TryParse("Red", out red))
    {
        Console.WriteLine(red);
    }
    else
    {
        Console.WriteLine("Could not translate to a valid enum");
    }

    if (Enum.TryParse("Purple", out purple))
    {
        Console.WriteLine(purple);
    }
    else
    {
        Console.WriteLine("Could not translate to a valid enum");
    }
}

Which produces:

Another benefit of this method over Parse is that it works with generics and that means you do not need to pass the Type parameter in and cast the return value as you had to do with Parse!

Note: This post is part of a series and you can find the rest of the parts in the series index.

I would guess strings are the most used type in .NET, so it is great to see some small improvements with them in .NET 4.

IsNullOrWhiteSpace

Since .NET 2.0 we have had the very useful IsNullOrEmpty which let us check for empty strings, but what about strings that contained nothing but white space? Unfortunately that would not be identified as empty! With .NET 4 we have a new method, IsNullOrWhiteSpace, which checks if a string is null, empty and if it is not just white space! Example usage:

string nullString = null;
string emptyString = string.Empty;
string blankString = emptyString.PadRight(30, ' ');
string notBlankString = "SADev.co.za";

Console.WriteLine("IsNullOrEmpty");
Console.WriteLine("\t nullString is: {0}", string.IsNullOrEmpty(nullString));
Console.WriteLine("\t emptyString is: {0}", string.IsNullOrEmpty(emptyString));
Console.WriteLine("\t blankString is: {0}", string.IsNullOrEmpty(blankString));
Console.WriteLine("\t notBlankString is: {0}", string.IsNullOrEmpty(notBlankString));

Console.WriteLine("IsNullOrWhiteSpace");
Console.WriteLine("\t nullString is: {0}", string.IsNullOrWhiteSpace(nullString));
Console.WriteLine("\t emptyString is: {0}", string.IsNullOrWhiteSpace(emptyString));
Console.WriteLine("\t blankString is: {0}", string.IsNullOrWhiteSpace(blankString));
Console.WriteLine("\t notBlankString is: {0}", string.IsNullOrWhiteSpace(notBlankString));

This produces

 

The important one to note is blankString, in the second set (line 15 of the code) has a different result compared to it’s result in the first set.

Join & Concat

Join allows us to concatenate an array of strings together with a specific separator character in place. For example:

string[] someValues = { "This", "is", "a", "list", "of", "strings" };
Console.WriteLine(string.Join(Environment.NewLine,someValues));

This produces

Concat does the same thing, except there is no separate character. Example:

string[] someValues = { "This", "is", "a", "list", "of", "strings" };
Console.WriteLine(string.Concat(someValues));

This produces:

Both these methods fails when we start working with generic lists, like List<T> as they were not supported. This meant you often ended up calling .ToArray on the list and taking the performance impact. Now new overloads have been added to string which cater for IEnumerable<T> so we no longer need to ToArray the list. Now we can pass the list directly in, as in the following example:

List<string> someValues = new List<string>() { "This", "is", "a", "list", "of", "strings" };
Console.WriteLine(string.Join(Environment.NewLine, someValues));

Welcome to part one of a new series of blog posts which will cover what is new in .NET 4. To be different I am not looking at the big features, like WF 4 or the super cool parallel stuff. This series will cover the smaller features, like new methods on existing classes or whole new classes which have been added. As with all series I do, you can see the rest of the post in the series on the series index.

We’ll start off with TimeSpan, which has been around since .NET 1.0 and represents a time interval (duration of time or elapsed time) that is measured as a positive or negative number of days, hours, minutes, seconds, and fractions of a second. So what is new in TimeSpan for .NET 4?

Parse & TryParse

Parse & TryParse are methods which have been around since the beginning and let you input a string in a specific format [-][d’.’]hh’:’mm’:’ss[‘.’fffffff]. and get a TimeSpan object back. For example:

TimeSpan oneFranctionSecond = TimeSpan.Parse("0.00:00:00.1");
TimeSpan oneHour = TimeSpan.Parse("1:00");
TimeSpan oneThousandDaysPast = TimeSpan.Parse("-1000.00:00");
Console.WriteLine(oneFranctionSecond);
Console.WriteLine(oneHour);
Console.WriteLine(oneThousandDaysPast);

This produces:

What is new in parsing? The ability to add in culture information through IFormatProvider. Why is this important? Because not everyone formats numbers the same. For example:

CultureInfo us = CultureInfo.GetCultureInfo("en-us"); // America
CultureInfo rm = CultureInfo.GetCultureInfo("rm"); // No idea, but it has my initials ;)
CultureInfo za = CultureInfo.GetCultureInfo("en-za"); // South Africa

string usResult = string.Format(us, "{0:N}", 100000);
string rmResult = string.Format(rm, "{0:N}", 100000);
string zaResult = string.Format(za, "{0:N}", 100000);

Console.WriteLine("America:\t {0}", usResult);
Console.WriteLine("RM:\t\t {0}", rmResult);
Console.WriteLine("South Africa:\t {0}", zaResult);

Produces:

See how all three locations have different formats, and this is important because the old methods couldn’t cope with these differences in numbers - they could only accept a single specific format.

Now we can do the following:

CultureInfo us = CultureInfo.GetCultureInfo("en-us"); // America
CultureInfo ru = CultureInfo.GetCultureInfo("ru-RU"); // Russia

TimeSpan oneFranctionSecondUS = TimeSpan.Parse("6:12:14:45.3448", us);
TimeSpan oneFranctionSecondRU = TimeSpan.Parse("6:12:14:45,3448", ru);

Console.WriteLine(oneFranctionSecondUS);
Console.WriteLine(oneFranctionSecondRU);

Note the comma in the Russian formatting, if you tried this in .NET 3.5 or before you would’ve gotten a FormatException but now it works!

ParseExact & TryParseExact

These are two brand new methods which let us specify the format string to use. Until now we have had to make sure we complied with: [-][d’.’]hh’:’mm’:’ss[‘.’fffffff].

Now we do not need to comply with a single format. We have two options with the format string either a build in one or a custom one. The built in ones are:

• c/t/T : These three do the same and this is what we are used to currently, namely: [-][d’.’]hh’:’mm’:’ss[‘.’fffffff].
  • Examples:
    • TimeSpan.Zero -> 00:00:00
    • New TimeSpan(0, 0, 30, 0) -> 00:30:00
    • New TimeSpan(3, 17, 25, 30, 500) -> 3.17:25:30.5000000
• g: The cultural sensitive short format. This is basically the same as c but the format provider supplied will be respected where c ignores it: [-][d’:’]h’:’mm’:’ss[.FFFFFFF].
  • Examples:
    • New TimeSpan(1, 3, 16, 50, 500) -> 1:3:16:50.5 (en-US)
    • New TimeSpan(1, 3, 16, 50, 500) -> 1:3:16:50,5 (fr-FR)
    • New TimeSpan(1, 3, 16, 50, 599) -> 1:3:16:50.599 (en-US)
    • New TimeSpan(1, 3, 16, 50, 599) -> 1:3:16:50,599 (fr-FR)
• G: The cultural sensitive long format in which there is no optional items, except the negative symbol: [-]d’:’hh’:’mm’:’ss.fffffff.
  • Examples:
  • New TimeSpan(18, 30, 0) -> 0:18:30:00.0000000 (en-US)
  • New TimeSpan(18, 30, 0) -> 0:18:30:00,0000000 (fr-FR)

We also have custom ones now, so we can really tweak it and this will be great for interoperability. I am not going to list all the parts as there is a lot, but every individual component is covered. Some examples of what we can now do are:

TimeSpan oneFranctionSecond = TimeSpan.ParseExact("1", "%F", CultureInfo.CurrentCulture);
TimeSpan oneMinuteThirtySeconds = TimeSpan.ParseExact("1:30", @"%m\:%s", CultureInfo.CurrentCulture);
TimeSpan oneDay = TimeSpan.ParseExact("1", "%d", CultureInfo.CurrentCulture);
TimeSpan oneDayAndTwoHours = TimeSpan.ParseExact("1=2", @"%d\=%h", CultureInfo.CurrentCulture);            

Console.WriteLine(oneFranctionSecond);
Console.WriteLine(oneMinuteThirtySeconds);
Console.WriteLine(oneDay);
Console.WriteLine(oneDayAndTwoHours);

Which produces:

My first time presenting at DevDays was a great experience with me presenting in the community slot. I told the attendees of my session that they were the smart ones because  being at the end of the day, only the dedicated people were left and those dedicated people got two presentations for the price of one timeslot.

The session itself covered how writing JavaScript easier with jQuery and Visual Studio 2010 which you can see below. Now the slides below are not being done using some special PowerPoint to web tool, but are HTML which uses jQuery. Using the same technology as I was presenting on and building it in Visual Studio 2010 really highlighted how powerful and easy this was to do. To navigate the slides click the grey dots at the top or click on the slide and press = to go forward and – to go back.

They are a little wide for the website, so to see them in a new window click here

The demo used jQuery and Visual Studio 2010 to clean up the page, and then connect to StackOverflow to pull down my stats and display them to the audience. The completed demo code (which is not included above, so the demo page won’t work) is as follows (this goes in the HEAD tags in demo .html page):

<script src="jQuery/jquery-1.4.2.js" type="text/javascript"></script>

<script type="text/javascript"> 
$(document).ready(function () {
  $("#DemoButton").click(gapSO);
});

function gapSO(e) {
///<summary>Gets and parses Stack Overflow Points</summary>
  var sourceDiv = $(this);
  var replacementText = "I have ";
  var stackOverflowURL = "http://stackoverflow.com/users/flair/53236.json";
  sourceDiv.html("Loading...");
  $.getJSON(stackOverflowURL, function (data) {
    replacementText += data.reputation + " points and " + data.badgeHtml + " badges on StackOverflow";
    sourceDiv.html(replacementText);
  });
};
</script>