Posts tagged ‘C#.NET’

Plain ol’ XML

So let’s say you are working on an application in the .NET sphere of influence, and you have an object that you want to turn into XML. However, you shoot it through an XmlSerializer and you think you are done.

Ugh, what’s all that cruft in the XML stream?

Well there are some options you can play with to get rid of the extra stuff and just get plain ol’ XML. Here is a code snippet, where you will pass in your own object instead of the generic Order as shown below:

public String GetPlainOldXML(Order order)
{
    var emptyNamepsaces = new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty });
    var settings = new XmlWriterSettings();
    settings.OmitXmlDeclaration = true;
 
    XmlSerializer xsSubmit = new XmlSerializer(typeof(Order));
    var xmlString = "";
    using (var sww = new StringWriter())
    {
        using (XmlWriter writer = XmlWriter.Create(sww, settings))
        {
            xsSubmit.Serialize(writer, order, emptyNamepsaces);
            xmlString = sww.ToString();
        }
    }
 
    return xmlString;
}

BTW, Happy Birthday to Leslie West of Mountain fame.

Error 404 on web service with map route

If you are getting an error 404 on your web service with a map route decorator on your methods, you might want to check your IIS settings to make sure that it is configured correctly.

Apparently, your app pool must be set up in integrated mode as opposed to classic mode in order for the routing to work.

BTW, Happy 10th Anniversary to the iPhone.

The final word on .NET background processing (for now)

While snooping around for information on .NET background processing, I came across a bunch of interesting articles by .NET MVP Stephen Cleary that go into great detail about using Task.Run vs. a BackgroundWorker control. Here is the link to the introduction of the series of articles:

Task.Run vs BackgroundWorker: Intro

BTW, I am impressed so far with the content that was revealed at the WWDC 2015 conference. I have been going through the presentations and, while there were no “knock your socks off” moments, there is still a ton of great stuff that they are packing into the new versions of iOS, OS X, and watchOS.

Cross a bridge at night

OK, here is a scenario. Four people on a journey together need to cross a bridge at night as quickly as possible. Among the four of them, they have one flashlight. They cannot continue their journey until all four reach the other side together. Since the bridge is narrow and slippery, and it is pitch black out being night and all, they decide to have two people cross with the flashlight, then one person returns with the flashlight back to the original side, and they continue until everyone is on the other side.

Oh, and also, the people can all walk at different paces, so when two people cross together, it takes them the amount of time that it takes the slower person to cover the distance.

For example, let’s say that the four people that need to cross can cover the distance of the bridge in 1 minute, 2 minutes, 5 minutes, and 10 minutes. What would be the shortest possible time?

The naive solution would be to have the 1 minute person be the primary flashlight runner and send them with the 2 minute person, return, then the 5 minute person, return, and finally cross with the 10 minute person, for a grand total of 19 minutes.

Now of course this is not the optimal solution, but more on that in a minute.

So how would we design an algorithm to solve this problem? Conventional wisdom says to create some kind of tree where you iterate through all of the possible combinations of initial crossings, then off those branches, combinations of reverse crossings, etc. Then once the tree is built, you can walk to all the branch tips and calculate the times, and then just display the shortest time.

But why do something logical? With all this computing power, I say that we implement my favorite algorithm for producing solutions to problems… The Monte Carlo method.

Here is the code for a C# .NET console app I threw together to solve this issue:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace BridgeAtNight
{
    public class BridgeState
    {
        public List<int> peopleOnLeft;
        public List<int> peopleOnRight;
        public int totalTime;
        public string peopleMovement;
 
        public BridgeState(int[] people)
        {
            totalTime = 0;
            peopleMovement = "";
            peopleOnLeft = new List<int>(people);
            peopleOnRight = new List<int>();
        }
 
        public void MoveLeftToRight(int leftToRight1, int leftToRight2)
        {
            peopleMovement = peopleMovement + string.Format("{0}>> {1}>> ", leftToRight1, leftToRight2);
            totalTime += Math.Max(leftToRight1, leftToRight2);
 
            peopleOnRight.Add(leftToRight1);
            peopleOnRight.Add(leftToRight2);
            peopleOnRight.Sort();
 
            peopleOnLeft.Remove(leftToRight1);
            peopleOnLeft.Remove(leftToRight2);
        }
 
        public void MoveRightToLeft(int rightToLeft)
        {
            peopleMovement = peopleMovement + string.Format("{0}<< ", rightToLeft);
            totalTime += rightToLeft;
 
            peopleOnLeft.Add(rightToLeft);
            peopleOnLeft.Sort();
 
            peopleOnRight.Remove(rightToLeft);
        }
 
        public void SolveWithNaivete()
        {
            peopleOnLeft.Sort();
            while (peopleOnLeft.Count > 1)
            {
                // move 2 people from the left to the right
                int leftToRight1 = peopleOnLeft[0];
                int leftToRight2 = peopleOnLeft[1];
                MoveLeftToRight(leftToRight1, leftToRight2);
 
                // move 1 person from right to left if there are any remaining people on the left
                if (peopleOnLeft.Count > 0)
                {
                    int rightToLeft = peopleOnRight[0];
                    MoveRightToLeft(rightToLeft);
                }
            }
 
            Console.WriteLine("Solution with naivete:");
            Console.WriteLine(string.Format("Time: {0} minutes", totalTime));
            Console.WriteLine(string.Format("Sequence: {0}", peopleMovement));
        }
 
        public void SolveRandomly()
        {
            Random rnd = new Random();
            while (peopleOnLeft.Count > 1)
            {
                // move 2 people from the left to the right
                var leftToRightRandom = peopleOnLeft.OrderBy(x => rnd.Next()).Take(2).ToList();
                int leftToRight1 = leftToRightRandom[0];
                int leftToRight2 = leftToRightRandom[1];
                MoveLeftToRight(leftToRight1, leftToRight2);
 
                // move 1 person from right to left if there are any remaining people on the left
                if (peopleOnLeft.Count > 0)
                {
                    var rightToLeftRandom = peopleOnRight.OrderBy(x => rnd.Next()).Take(1).ToList();
                    int rightToLeft = rightToLeftRandom[0];
                    MoveRightToLeft(rightToLeft);
                }
            }
        }
    }
 
    class Program
    {
        static void Main(string[] args)
        {
            BridgeState naiveBridgeState = new BridgeState(new int[] { 1, 2, 5, 10 });
            naiveBridgeState.SolveWithNaivete();
 
            List<string> bestTimeResults = new List<string>();
            int bestTime = 999999;
            for (int idx = 1; idx < 1000000; idx++)
            {
                BridgeState randomBridgeState = new BridgeState(new int[] { 1, 2, 5, 10 });
                randomBridgeState.SolveRandomly();
                if (randomBridgeState.totalTime < bestTime)
                {
                    Console.WriteLine(string.Format("Better random solution found in pass {0}:", idx));
                    Console.WriteLine(string.Format("Time: {0} minutes", randomBridgeState.totalTime));
                    Console.WriteLine(string.Format("Sequence: {0}", randomBridgeState.peopleMovement));
                    bestTime = randomBridgeState.totalTime;
                    bestTimeResults = new List<string>();
                    bestTimeResults.Add(randomBridgeState.peopleMovement);
                }
                else if (randomBridgeState.totalTime == bestTime)
                {
                    if (!bestTimeResults.Contains(randomBridgeState.peopleMovement))
                    {
                        Console.WriteLine(string.Format("Sequence: {0}", randomBridgeState.peopleMovement));
                        bestTimeResults.Add(randomBridgeState.peopleMovement);
                    }
                }
            }
 
            Console.WriteLine("Press any key to exit the application");
            Console.ReadKey();
        }
    }
}

There are undoubtedly some optimizations I can make to this code above, such as ordering the times in the MoveLeftToRight function. However, I was kind of surprised to see this run, as sometimes the optimal solution of 17 minutes was found in the first few thousand random walk throughs, and other times it would take a few hundred thousand walk throughs before the 17 minute solution was found. To me, it did not seem like there were enough different combinations that would make it so difficult to randomly find the solution.

For those who cannot/will not run this code, the crux of the biscuit, given the times of the walkers above (1 minute, 2 minutes, 5 minutes, and 10 minutes), is to send the slowest people across together once there is someone faster on the other side. Or in other words, first send 1 and 2 across, then have 1 come back. Then, send 5 and 10 across, and have 2 come back. Then 1 and 2 make the final crossing.

BTW, Happy Talk Like A Pirate Day today.

How to use a C# .NET interface to send messages between classes

I have used delegates in Objective-C to send message back and forth between classes for years. (And in fact, I did a blog post on Setting up an Objective-C delegate for the iPhone SDK a few years back on this very subject.) Indeed, delegates are a critical part of the Objective-C language, as it is usually good for objects to be able to let other objects know what is going on.

Well now, in my .NET development duties, I have a very similar situation. My code has a bunch of user controls that I use, and I need to have messages sent from one user control to another as the user works with the various pieces of the application.

Of course, in order to keep the compiler happy and get it working, you can do something quick and dirty like putting in an instance variable into the class that points back to your user control, and then when you need to let that user control know what is going on, just use the instance variable reference to call a method in that user control’s class.

But this is not scalable. If you have a bunch of different user controls calling a specific user control, you would have to put a reference to each different type of calling control, and then walk through them and determine which one you need to call in each case.

C# interface to the rescue. By using a C# interface, you can put an instance variable for your interface into your called class, which will then allow your calling class (which of course follows the interface) to have a method fired in it.

Here is a tutorial using C# for a console application that demonstrates the principles:

using System;
 
namespace ConsoleApplication1
{
    interface IMyClass  // 1
    {
        void PassMessage(string theMessage);
    }
 
    public class MyClass  // 2
    {
        private IMyClass parentClass;  // 3
 
        public void SetParentClass(object c)  // 4
        {
            parentClass = c as IMyClass;
        }
 
        public void Nudge()  // 5
        {
            parentClass.PassMessage("MyClass hath been nudged.");
        }
    }
 
    public class MainClass : IMyClass  // 6
    {
        public void DoStuff()  // 7
        {
            Console.WriteLine("About to DoStuff in MainClass");
            var c = new MyClass();
            c.SetParentClass(this);
            c.Nudge();
 
            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();
        }
 
        public void PassMessage(string theMessage)  // 8
        {
            Console.WriteLine("Message passed from MyClass: " + theMessage);
        }
    }
 
    public class Program
    {
        static void Main(string[] args)
        {
            var mainClass = new MainClass();
            mainClass.DoStuff();
        }
 
    }
}

So let’s break this down a bit. The numbers below correspond to the comments in the code above.

1. This is the interface definition. You need to put in here a listing of the methods that you want to be calling, sort of like an abstract class.

2. This is the class definition for the called class, or the class that needs to send a message back to the calling class.

3. Here is where the reference back to the calling class is kept. Since it’s type is an interface, any object that follows that interface can receive the caller’s message.

4. In this method, I am setting the reference back to the calling class. You can do this in the constructor as well if desired.

5. The Nudge method is a method in the called class that when executed, needs to send a message back to the calling class.

6. This is the class definition for the calling class. Notice that it follows the interface above, which requires that you provide the method specified in the interface.

7. This method creates the called class and sets up the interface reference, and then sends the Nudge message to the called class, which in turn calls back by firing the PassMessage method.

8. Here is where I do the processing necessary when the calling class is sending the message.

This is a pretty trivial example, but it should give you an idea on how to start setting up more complex cases.

BTW, Happy Birthday to John Myung, the fantastically talented bass player and founding member of Dream Theater. They are playing in a town near me this spring, but unfortunately I will be out of town and unable to see them. Great sadness.

.NET regex to find strings inside curly braces

Regular expressions all by themselves have the magical ability to amaze and confound all at the same time. Throw in a dash of .NET string interpretation and you have a recipe for pulling out the remaining hair that you might have on your head.

So I was trying to use a regex to do some searching inside of a large string for strings inside curly braces, such as {this} and {these three words}. My string matching routine would return “this” and “these three words”, without the quotes of course. It took a bit of trial and error, but here is the important stuff for the routine that I put together to accomplish this task:

const string pattern = @"\{([^\}]+)\}";
foreach (Match match in Regex.Matches(theLargeString, pattern))
{
    Console.WriteLine("Found a field match: " + match);
}

BTW, a special birthday shout out to one of the mega stars of our generation, who turns 50 years young today. Happy birthday, Larry The Cable Guy.

Overriding a TargetType Style without a Key in WPF

I have been doing a lot of work in WPF lately, and it is a different animal.

The default styles of a button did not look right for my application, so I came up with the following XAML that styles up all of the button objects in my application:

<Style TargetType="{x:Type Button}">
    <Setter Property="SnapsToDevicePixels" Value="true"/>
    <Setter Property="OverridesDefaultStyle" Value="true"/>
    <Setter Property="Background" Value="CornflowerBlue" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type Button}">
                <Border x:Name="Border" CornerRadius="0" BorderThickness="0" 
                            Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding Background}">
                    <ContentPresenter Margin="2" HorizontalAlignment="Center" VerticalAlignment="Center" RecognizesAccessKey="True" />
                </Border>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsMouseOver" Value="true">
                        <Setter TargetName="Border" Property="Background" Value="#4667A5" />
                    </Trigger>
                    <Trigger Property="IsPressed" Value="true">
                        <Setter TargetName="Border" Property="Background" Value="#3C588C" />
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter TargetName="Border" Property="Background" Value="LightGray" />
                        <Setter TargetName="Border" Property="BorderBrush" Value="#AAAAAA" />
                        <Setter Property="Foreground" Value="DarkGray"/>
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="true">
                        <Setter Property="Foreground" Value="White"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

As you can see, I am using TemplateBinding to bind to the desired background color.

However, in one of my user controls, I want to be able to change the background color of the button in certain situations. Initially, I just created a copy of the above XAML, gave it a Key, and then used that key name to style up the Buttons that I wanted to.

As always, there is a better way. I found that there was a way to use a BasedOn in my new style to pull in the style from the global resources and just change what I needed, here is what it looks like:

<Style x:Key="SpecialButton" TargetType="Button" BasedOn="{StaticResource {x:Type Button}}">
    <Setter Property="Width" Value="20" />
    <Setter Property="Visibility" Value="Collapsed" />
    <Setter Property="Content" Value=">" />
    <Setter Property="IsTabStop" Value="False" />
    <Setter Property="Background" Value="LightGray" />
</Style>

BTW, Happy Birthday to Eugene Levy, by far one of the funniest actors out there.

DBNull string field handling

Let’s say for the sake of argument that you are using a SQL Server Compact database in your C# .NET application, and your User table has nvarchar fields that are nullable, and your User class doesn’t care if those fields are null, it just wants empty strings instead.

Sadly to say, you are eventually going to end up with nulls in those fields, and as a result, if you use a SqlCeDataReader to step through a record set, this kind of stuff will (at some point) give you a runtime error:

myUser.UserName = (string)dataReader["UserName"]);

So I started looking for the best way to handle this problem. What I didn’t want to do was this for every single string field assignment:

myUser.UserName = (System.DBNull.Value == dataReader["UserName"] ? "" : dataReader["UserName"]);

This seems a bit wasteful to me, as the data reader is accessed twice. Sure, I could have encapsulated this into a function to pretty up the code a bit, but that would just be hiding the ugliness. Then, it occurred to me to try the Convert class to see what would happen, and it turns out that this code knows how to convert a DBNull to an empty string:

myUser.UserName = Convert.ToString(dataReader["UserName"]);

The Convert class may in fact do the same thing as I have shown above, but I would hope that Microsoft would make their built in function better than something that I would just hack together.

BTW, I hope everyone out there has voted, this is an important election. (Finally, tomorrow I can watch TV or get the mail without being bombarded by increasingly stupider campaign and “issue” advertisements.)

How to dynamically generate a TrackBallInfoTemplate

The Telerik ChartView control is nice, but if you cannot create your XAML ahead of time (or in other words, you don’t know how many LineSeries you are going to have on your chart), then you are in uncharted territory. Especially if you are not super solid in WPF and data binding as I am.

Using their example code, I was able to get the track ball info to show the date and value of the data points (basically the X and Y values of the data point), but instead I wanted to show a label for that LineSeries along with the Y value. Initially I tried to use a DataTemplate in the Resources of my user control, but I could not get the binding to work the way I wanted to.

Finally, to solve this issue, I had to resort to build the XAML in my code and set the TrackBallInfoTemplate. Here is what it looks like:

// the class holding the data for the chart...
public class SalesInfo
{
    public string Employee { get; set; }
    public DateTime Time { get; set; }
    public int Value { get; set; }
}
 
// then, further on down the code...
Color[] colorArray = { Colors.Red, Colors.Green, Colors.Blue, Colors.Yellow };
 
// and...
data = new RadObservableCollection(data.OrderBy(x => x.Time));
Color dataColor = colorArray[loopCounter % 4];
LineSeries line = new LineSeries();
line.Stroke = new SolidColorBrush(dataColor);
line.StrokeThickness = 2;
line.CategoryBinding = new PropertyNameDataPointBinding() { PropertyName = "Time" };
line.ValueBinding = new PropertyNameDataPointBinding() { PropertyName = "Value" };
line.ItemsSource = data;
 
StringBuilder templateString = new StringBuilder();
templateString.Append("<DataTemplate xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'>");
templateString.Append("<StackPanel Orientation='Horizontal'>");
templateString.Append("<TextBlock Text='" + u + "' />");  // u refers to the name of this line series (Employee)
templateString.Append("<TextBlock Text=': ' />");
templateString.Append("<TextBlock Text='{Binding DataPoint.Value}' />");
templateString.Append("</StackPanel>");
templateString.Append("</DataTemplate>");
 
var xml = XmlReader.Create(new StringReader(templateString.ToString()));
var tbiTemplate = (DataTemplate)XamlReader.Load(xml) as DataTemplate;
line.TrackBallInfoTemplate = tbiTemplate;
myTelerikChartView.Series.Add(line);

And so now, here is what my chart view looks like with the customized track ball info:

BTW, Happy Birthday to Ty Tabor.

EDIT: I would like to take a moment to say thanks to Yavor from Telerik, he responded to my posting on the Telerik forums and pointed out that the DataPoint object has a DataItem object child that is the object that created the DataPoint. As a result, in my XAML Resources, I can bind to DataPoint.DataItem.Employee, and it works as expected. Here is that link:

Creating LineSeries programmatically with custom TrackBallInfoTemplate

Using the new WPF themes

So I am looking around for some ideas on making this WPF based application for Windows that I am working on look slightly less sucky. And I see some nifty themes on this web page:

WPF Themes

And I am thinking that would be pretty cool to just swap in one line in the App.xaml file, and my whole app would look different.

Cool in theory, but some implementation details are a bit fuzzy.

Here is what I did to get it working with VS 2010 Ultimate:

  • Install the WPF Toolkit by clicking on the big purple “download” button on the above web site
  • Download the themes xaml files by going to this web site: WP Futures (scroll down to WP Themes and click the link to download the zip file)
  • Unzip the downloaded file and add the needed xaml files to your WPF project
  • Add a reference to WPF Toolkit in your application’s References folder
  • Add a ResourceDictionary line to the Application.Resources section of your App.xaml file to make it look like the one shown on the WPF Themes page above

Keep in mind that if you put your xaml theme files in a folder off the root of your project, you will need to adjust the Source property of the ResourceDictionary. For example, I put the xaml theme files in a Themes folder off the root of the project, so the Source for me looks like this:

<ResourceDictionary Source="/Themes/ExpressionDark.xaml" />

BTW, Happy Birthday to John Petrucci, who is quite clearly not a native of this planet.