My technical blog

Various thoughts on my work with .NET technologies (and more)

[geodanila]

AutocompleteSearchBox - Custom search control for Windows Store Apps

After starting a new project I found myself in need of a custom SearchBox control implementation for Windows Store Apps that would display results in a popup and filter them as I type. Since I found no implementation that matched my needs I decided to build a custom control.

The resulting implementation can be found on GitHub at the following link. I'll walk you through several use cases for the custom control and explain several decisions I had to make in order for the control to behave as expected.

The custom control exposes four dependency properties, namely: ItemsSource, Filter, ItemTemplate and QueryText.

The ItemSource property is used for the entire collection of possible results for the search box. This collection can be filtered using the Filter dependency property

The Filter property is a function whose arguments are the current item being checked against the filter, the filter text, the function returning true if the item should be displayed in the search results. The default Filter checks the ToString() representation of each object in the ItemsSource against the QueryText. The ItemsSource also offers support for observable collections.

The ItemTemplate property is used to render each result in the results list box.

The QueryText property holds the current query text of the search box.

AutocompleteSearchBox also exposes two routed events: SearchResultSelected called when one of the results has been picked from the results list via keyboard, mouse or touch. The second event is QueryChanged is called each time the QueryText changes.

Implementation details are pretty straightforward, although I feel a certain decission has to be explained regarding the XAML implementation.

You might notice the fact that the results list box is contained within a Canvas control of 0 weight and height. This was required due to the fact that the list box should behave similar to a pop-up, and the Popup control was not added to the Windows Store App stack (not as WPF developers knew it at least) - The Canvas control does not clip child elements to its bounds and this makes the list box seemingly float.

So, feel free to use my implementation in your applications and have fun coding.

[geodanila]

OpenCover, an excellent alternative to Visual Studio’s code coverage tool

The project I'm currently working on places a heavy emphasis on having a high percentage of the code covered by unit tests. As you may already know, Visual Studio provides a decent code coverage tool integrated into the IDE.

The problem...

Visual Studio's tool comes with a number of issues:

The lack of customizing what code gets checked for coverage besides the limited ExcludeFromCodeCoverageAttribute.

The lack of basic user interaction features like having the ability to filter the list of results produced by the tool.

The faulty computation of code coverage for code that makes use of the async and await keywords that has already been reported numerous times (StackOverflow, Microsoft Connect #1, Microsoft Connect #2)

The fact that this feature is only available for the commercial versions of Visual Studio.

With this in mind I decided to try OpenCover, an open-source project that seeks to provide precise code coverage information for .NET code licensed under the MIT Licence.

Integrating OpenCover in our existing project took around a couple of hours and produced excellent results and feedback from my team mates. These are the steps I followed in order to get everything running:

Right-click your solution in Solution Explorer and choose Manage NuGet Packages - Install the OpenCover and the ReportGenerator NuGet packages at solution level (no need to actually add these packages to any project, we need them here for ease of use)

Create a Windows batch file (or a Powershell script if that's your thing) that will contain the following lines:

Create a "coverage\MSTest" directory in the solution's root folder if it doesn't already exist: if not exist "%CD%\coverage\" mkdir "%CD%\coverage\" if not exist "%CD%\coverage\MSTest" mkdir "%CD%\coverage\MSTest

Delete any file in this directory if it exists: del "%CD%\coverage\MSTest\*.*" /F /Q

Rebuild your solution in order to have the latest .PDB file in line with the code (this is required for OpenCover to work correctly): "C:\Program Files (x86)\MSBuild\12.0\Bin\MSBuild.exe" FooBar.sln /p:Configuration=Debug /v:minimal /t:rebuild

Run the OpenCover console using the MSTest test runner on the assemblies containing the unit tests: "./packages/OpenCover.4.5.3723/OpenCover.Console.exe" -register:user -target:"C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE\MSTest.exe" -targetargs:"/noisolation /testcontainer:"%CD%/ProjectOne.Tests/bin/Debug/ProjectOne.Tests.dll" "%CD%/ProjectTwo.Tests/bin/Debug/ProjectTwo.Tests.dll" /resultsfile:%CD%\coverage\MSTest\FooBar.trx" -excludebyattribute:*.ExcludeFromCodeCoverage* -filter:"+[*]FooBar.* -[*.Tests]*" -mergebyhash -skipautoprops -output:%CD%\coverage\MSTest\FooBarReport.xml Use the -filter argument to specify what code needs to be checked for coverage and what code is excluded. (See the official documentation for more information)

Run the ReportGenerator tool to get a nice looking report: "./packages/ReportGenerator.2.1.4.0/ReportGenerator.exe" -reports:"%CD%\coverage\MSTest\FoorBarReport.xml" -targetdir:".\coverage

And finally, open the report page with your favorite browser: start file://%CD%\coverage\index.htm

I also created a small Visual Studio plug-in that executes this batch file for ease of use.

Bear in mind all of the file paths for executables such as MSTest and MSBuild work for Visual Studio 2013. Other versions might have different locations for these executables.

In conclusion OpenCover proved to be superior to Visual Studio's implementation by being a lot more flexible in deciding what code gets checked for code coverage due to the filter argument, by giving accurate metrics results, even for the async and await keywords and by providing a better UI that allows the user to search in the generated report

[geodanila]

Parallel delegate execution using Tasks

While implementing the logic for a new app our team is working on, one of my colleagues encountered the following problem:

He wanted to implement a method that had to perform a series of parallel web service calls and continue the execution of the method once all of the calls have completed. Since we make extended use of the async / await constructs we decided that we needed a helper method that could accept a series of delegates and that returned a Task.

The Task.WhenAll method accepts a series of tasks as input and returns a Task that is marked as completed once all of the tasks are completed.

The method creates a new Task for each provided delegate and passes this series of tasks to the WhenAll method. See the following example for usage:

Need to pass parameters to your actions? Use a lambda expression:

[geodanila]

Multiple values as Dictionary keys in .NET

Need to have a multiple key dictionary? Simple, use the System.Tuple type.

Take care though, this solution will only work as long as the types used in the tuple are value types as well.

Consider the following example:

Redefining what makes two Foo objects equal, by overriding the Equals method, can lead to the desired behaviour of using the class inside a Tuple as part of a Dictionary's key.