WPF MVVM project template

This extension will add a Visual Studio 2010 project template to create a WPF client application with MVVM pattern project structure.

(after installing the .vsix you’ll need to restart Visual Studio).

the new project template can be found under: File -> New -> Project -> C# templates.
it is called “WPF MVVM Application”.

the new project have an MVVM folders and classes structure with some randomly generated data and a simple view.

download from HERE

C# random helper class

Very often i make an ‘offline’ application in order to work faster without the need to compile the whole big-mama application.
as it name suggest an ‘offline’ app does not have a database to work with so i need to mock some data.
with some code borrowed from this blog post the below C# random helper class can be used in any application.
(if you have something to add drop a comment)

using System;
using System.Text;
using System.Windows.Media;

namespace WpfApplication1.Helper
{
    public static class RandomHelper
    {
        private static Random randomSeed = new Random();

        /// <summary>
        /// Generates a random string with the given length
        /// </summary>
        /// <param name="size">Size of the string</param>
        /// <param name="lowerCase">If true, generate lowercase string</param>
        /// <returns>Random string</returns>
        public static string RandomString(int size, bool lowerCase)
        {
            // StringBuilder is faster than using strings (+=)
            StringBuilder RandStr = new StringBuilder(size);

            // Ascii start position (65 = A / 97 = a)
            int Start = (lowerCase) ? 97 : 65;

            // Add random chars
            for (int i = 0; i < size; i++)
                RandStr.Append((char)(26 * randomSeed.NextDouble() + Start));

            return RandStr.ToString();
        }

        public static int RandomInt(int min, int max)
        {
            return randomSeed.Next(min, max);
        }

        public static double RandomDouble()
        {
            return randomSeed.NextDouble();
        }

        public static double RandomNumber(int min, int max, int digits)
        {
            return Math.Round(randomSeed.Next(min, max - 1) + randomSeed.NextDouble(), digits);
        }

        public static bool RandomBool()
        {
            return (randomSeed.NextDouble() > 0.5);
        }

        public static DateTime RandomDate()
        {
            return RandomDate(new DateTime(1900, 1, 1), DateTime.Now);
        }

        public static DateTime RandomDate(DateTime from, DateTime to)
        {
            TimeSpan range = new TimeSpan(to.Ticks - from.Ticks);
            return from + new TimeSpan((long)(range.Ticks * randomSeed.NextDouble()));
        }

        public static Color RandomColor()
        {
            return Color.FromRgb((byte)randomSeed.Next(255), (byte)randomSeed.Next(255), (byte)randomSeed.Next(255));
        }

    }
}

Silverlight: double click Trigger & call method Action

There are many different ways to implement double click in Silverlight, I chose to write it as a Trigger so it can be used anywhere and easily.

Of course you can write your own Action to use with that Trigger, but I wanted a most generic Action that will call a method and also could be used anywhere and easily.

The following Trigger (DoubleClick) & Action (InvokeMethodAction) classes act like any other event & handler. They can be used on any UIElement.

DoubleClick:

public class DoubleClick : TriggerBase<UIElement>
{
    private readonly DispatcherTimer _timer;
    private Point _clickPosition;

    public DoubleClick()
    {
        _timer = new DispatcherTimer
        {
            Interval = new TimeSpan(0, 0, 0, 0, 300)
        };

        _timer.Tick += OnTimerTick;
    }

    protected override void OnAttached()
    {
        base.OnAttached();

        AssociatedObject.MouseLeftButtonUp += new MouseButtonEventHandler(AssociatedObject_MouseLeftButtonUp);
    }

    void AssociatedObject_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        UIElement element = sender as UIElement;

        if (_timer.IsEnabled)
        {
            _timer.Stop();
            Point position = e.GetPosition(element);

            if (Math.Abs(_clickPosition.X - position.X) < 1 && Math.Abs(_clickPosition.Y - position.Y) < 1)
            {
                InvokeActions(null);
            }
        }
        else
        {
            _timer.Start();
            _clickPosition = e.GetPosition(element);
        }
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();

        AssociatedObject.MouseLeftButtonUp -= new MouseButtonEventHandler(AssociatedObject_MouseLeftButtonUp);
        if (_timer.IsEnabled)
            _timer.Stop();
    }

    private void OnTimerTick(object sender, EventArgs e)
    {
        _timer.Stop();
    }
}

InvokeMethodAction:

public class InvokeMethodAction : TargetedTriggerAction<UIElement>
{
    protected override void Invoke(object parameter)
    {
        if (MethodToInvoke != null)
        {
            MethodToInvoke(Target, null);
        }
    }

    public delegate void Handler(object sender, RoutedEventArgs e);
    public event Handler MethodToInvoke;

}

Download sample project here.

C# Dictionary get key from value

Here is a simple thing missing from the Dictionary class.

When you have a Dictionary:

Dictionary<string, object> SampleDict;

Getting the value by specifying a key is straight forward:

object obj = SampleDict[“someKey”];

But how do you get the key by specifying a value?
There is no such thing in the Dictionary class!
What you’ll usually do is loop the Dictionary to find the value and return its relevant key.
I have made it into an extension class so it can be used like any other Dictionary member:

using System;
using System.Collections.Generic;

namespace Utils
{
    public static class IDictionaryExtensions
    {
        public static TKey FindKeyByValue<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TValue value)
        {
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");

            foreach (KeyValuePair<TKey, TValue> pair in dictionary)
                if (value.Equals(pair.Value)) return pair.Key;

            throw new Exception("the value is not found in the dictionary");
        }
    }
}

And you use it like so:

String result = SampleDict.FindKeyByValue(someObject);

As you can see any type can be used with the Dictionary: IDictionary<TKey, TValue>