Detect when another site is unavailable. (404 detection)

A long time ago we used to store our code on punched cards.  Since that time, our development tools improved a lot.  Thanks to more powerful languages and tools, it became easier for us to write code, and as a result, our applications became more and more complex.  In 1986 Fred Brooks predicted exactly that in his article “No Silver Bullet”.  Today, any modern application uses third party libraries or components.  Our web apps need to integrate with other sites to use their services. But what do you do if the third party site is down?

At first, the problem doesn’t seem that difficult, but then I realized that it’s impossible to detect with JavaScript when another site is unavailable. (Please let me know if I’m wrong.)  If it would be possible to do this with client scripting, it would be huge security hole.  Since the release of Netscape Navigator 2.0 in 1996, browsers prevent access to most methods and properties across pages on different sites.  Today, this policy is known as Same Origin Policy.

The solution I came up with is to ping the third party host on the server side before JavaScript is loaded.  If I get a good response, then I proceed with my JavaScript; otherwise, it’s redirected to my error page.

Here’s a sample how you can check if the host available with ASP.NET:

protected void Page_Load(object sender, EventArgs e)
{
    HttpWebResponse response;
    try
    {
        var request = 
            (HttpWebRequest)WebRequest.Create("http://www.someSite.com/camdsa");
        response = request.GetResponse() as HttpWebResponse;
    }
    catch (WebException webException)
    {
        Response.Redirect("ErrorPage.aspx?status=" + webException.Status);
        return;
    }
}

If GetResponse() throws a WebException, it means that something went wrong with our request.  We can figure out what’s wrong by analyzing the WebException Status and Response properties.

Setting up RavenDB as an IIS application by pictures.

I’ve been living all my professional live in relational database world.  Lately NoSQL is making a lot of buzz that I couldn’t ignore it any more and decided to take a closer look.   The first question I had is which NoSQL database should I play with?  I narrowed my option to three: CouchDB, MongoDB, and RavenDB.  Being a .NET developer RavenDB looked like a logical choice. It’s .NET friendly and has a LINQ provider.

Next step for me was to download and install RavenDB and that what this post is about.

1. Download RavenDB. 

You can go to RavenDb’s download page or just click here to grab the latest build.

2. Unzip the file.

Use your favorite file archiving utility to unzip the file you just downloaded.  In my case I used 7-Zip to unzip RavenDB-Build-206.zip file.  By the way I decompressed the files intto C:\RavenDB folder.

3. Next let’s fire IIS Manager and create new application pool.

You need to open the IIS Manager.  The following instruction are for IIS 7.  If you are using different version than you’re on your own. 

In Connections panel select Application Pools.

Then in Actions panel click on the “Add Application Pool…” link.  If you clicked it correctly, you should see the “Add Application Pool” dialog.  In case you don’t see this dialog than you need to read How to Use a Computer Mouse.

You need to name the application pool and you must choose .NET Framework v.4.0 in the “.NET Framework version” drop down box.  Leave everything else the same and press the OK button.

 

4.  Create a new Raven Web Site.

In IIS Manager right lick on the Sites folder and select “Add Web Site…” from the context menu.

You should see the “Add Web Site” dialog. 

For Site name type “RavenWeb” or you can pick some other name.

Select RavenApplicationPool for Application pool.  You do that by click on Select button.

Make sure that Physical path is points to “Web” folder in extracted folder.  In my case it’s going to be “C:\RavenDB\Web”.

Leave everything the same except the Port.  I picked 8080 for my port you can type the same number or select different.

Your values should look similar to mine but don’t click the OK button yet.

Click the “Test Settings…” button and you probably will see that authorization failed.

We must provide the user for our site that has write access to the physical database location.  Close the “Test Connection” dialog and click on “Connect as…” button in the “Add Web Site”.

“Connect As” dialog should appear on your screen.  Select “Specific user” option and click on the “Set…” button to to enter credentials in “Set Credentials” dialog.

If you entered. proper credentials, than by pressing on the “Test Settings…” button you should see that Authentication and Authorization are valid and we’re ready for next step.

Press the “Close” button for “Test Connection” and then “OK” button for “Add Web Site” dialog.  You should see that the new Web Site was created.

 

5. Done.

We successfully installed and set up Raven DB to run in IIS.  Just navigate to http://localhost:8080 url or in IIS Manager make sure the new web site is selected and click on “Browse *:8080 (http)” link in Action section.  Rave DB page should be opened in your favorite browser.

NuGet Upgrade on 12/10/10

There’s a new upgrade for NuGet.  To update it just go to Tools –> Extension Manager in Visual Studio to lunch Extension Manager dialog. In Updates you’ll see an update for NuGet Package Manager.  It will ask you to restart your VS.

iPad and Russian Keyboard

Last week I got a present, a new shiny iPad.  After downloading and playing with few games, I decided it’s time for me to install a Russian keyboard even I don’t type much in Russian.  Like any Apple’s Mac Book, iPad has an option for Russian Phonetic keyboard.  If you don’t know what’s Russian Phonetic Keyboard, read my previous post on the subject.

In order to set up Russian Phonetic Keyboard, I start Settings application.  Then go to General | Keyboard | International Keyboards | Add New Keyboard….  I add Russian – Phonetic.

When I try to use the keyboard that I just added, I’m unpleasantly surprised.  It’s Russian standard keyboard but I explicitly was adding Phonetic one.

If I’m doing something wrong, can someone just slap me and let me know what an idiot I am and what I need to do install it correctly.  Also Apple made a grammatical error when they named the keyboard “Русская” instead of “Русский”.  Like in many other languages, in Russian objects have sex and “keyboard” is male in Russian.  By saying “Русская” it makes the keyboard a female and that sounds way wrong.  You expect this error from people why just started learning Russian.

UPDATE: Thanks to Sergey who reminded me about Russian translation for word “keyboard” which is “клавиатура”.  Клавиатура has female sex and this case “Русская” would be appropriate.  I’m so accustomed to use word “keyboard” even when I speak Russian.

Baby steps to create a NuGet Package.

You probably heard about NuGet (formally known as NuPack), an open source package management system for the .NET from Microsoft.  Jeff Kwak, who works with me at Ultimate Software, recently wrote a nice post about how to create a NuGet Pakage.  Jeff’s article inspired me to create a package for my own open source project, SystemWrapper.   In this post I want to describe step by step how I did it.

Step 1: Create a NuSpec file.

NuSpec file is an xml file that contains the metadata for a package.  I’ll try to describe every field of NuSpec format with an example.

In this first step we’ll going to use the minimum set of fields.

Element	Description
id	The identifier for the package.  It used as a partial name of the package.
version	The package version.  Also used as a partial name of the package.
authors	Author name.  Use a comma to separate multiple authors.
description	You know what it is.

<package>
  <metadata>
    <id>SystemWrapper</id>
    <version>0.3.5.0</version>
    <authors>Vadim Kreynin</authors>
    <description>
      SystemWrapper is a library that wraps .NET classes for system resources like System.IO.FileInfo, System.Reflection.Assembly, and many other classes so you can easily mock them.
    </description>
  </metadata>
</package>

I named the xml SystemWrapper.nuspec.  I believe that it is a good logical name for NuSpec file.

One of the way to add a package is to use Add Library Package Reference dialog.  I’ll talk more about adding a package and Add Library Package Reference dialog later in this article but for now I want to show where NuSpec fields a re used.  Bellow is the image that describes where above NuSpec metadata elements used in the dialog.

Step 2: Build the package.

First you need to download NuGet.exe command line tool.

Now when we have NuGet.exe, we are ready to create our SystemWrapper NuGet package.  Fire up your Command Console and type the following line.
NuGet.exe pack SystemWrapper.nuspec

If everything runs at it supposed to, you should see systemwrapper.0.3.5.0.nupkg file in your Windows Explorer.

As you can see the name of the file is [id].[version].nupkg.  id and version from our NuSpec file.

Step 3: Publish the package.

To release System Wrapper to the world we need to contribute to NuGet packages on CodePlex.  In this example I’m going to show how to host System Wrapper NuGet package locally.  You can follow this technic to host packages for your company.  I learned how to host NuGet packages locally from a great Phil Haack’s post.

First, I create a directory for my packages.  It has an original name ‘packages’.

Next, we need to add another package source.  Out of the box you should have only one package source which named ‘NuGet official package source’.  We are going to create another package source and I’m going to call mine ‘Vadim’s package source’.  I think that this is going to cement my legacy.

In order to add a package source in Visual Studio we need to go to Tools –> Options.  Inside the option dialog box select Package Manager and enter values for Name and Source and press Add button and then OK to close the Options dialog.

You also can get to this dialog by pressing Settings button in Add Library Package Reference dialog, which is the first image of this post.  The button located in the lower left corner of the dialog.

Step 4: Find the package in Visual Studio.

There are two ways we can browse for our package.  One way is using Package Manager Console which is Powershell based. Another one is Add Library Package Reference dialog that I mentioned earlier.

First let me describe how we can browse using Package Manager Console.  We can lunch the console by selecting View –> Other Windows –> Console from the menu or simply press Ctrl+W, Ctrl+Z.

After console is loaded, we need to select our package source.  Just pick it from the Package source drop down box.  In my case it’s “Vadim’s package source”.  Next, type List-Package at PM> prompt.  See the result bellow.

I don’t know why I cannot see my description in Package Manager Console.  It shows fine in Add Library Package Reference dialog.  Let me know if you have an answer for me.

Now let me show how you can browse for the package using Add Library Package Reference dialog.  The way I do it is just right click on References in the project to see my  add options.  Select “Add Library Package Reference…” to display the dialog.  The dialog has three panels.  The first panel has three sections: Installed packages, Online, and Updates.   “Installed packages” shows the package that installed for specific project.  The second one “Online” shows packages that are available.  We want to chose this option.  Select your package source.  The third option is updates.

The second panel shows the list of packages.  The third panel shows details of the selected package.

It doesn’t make scenes for us to install the package at the moment because we only describe the package but doesn’t add any libraries to the project.

Step 5: Add SystemWrapper.dll to the package.

Our goal is to add SystemWrapper to the project.  It means that we need to add assembly reference to SystemWrapper.dll. It’s very easy to do, we just need to add files element to our NuSpec file. files element must be on the same level as metadata element.

Here’s a fragment that we add to NuSpec metadata:

<files>
   <file src="SystemWrapper\bin\Release\*.dll" target="lib" />
</files>

file element has two attributes src and target.  I just want to let you know that src is a path that relative to the nuspec file.  Our target attribute has a value ‘lib’, it means that dlls under SystemWrapper\bin\Release will become assembly references on install.  In our case it’s going to be only one dll.  You can get more details on your own by reading the NuSpec File Element Specification.

Here’s the complete NuSpec file:

 

<package>
  <metadata>
    <id>SystemWrapper</id>
    <version>0.3.5.0</version>
    <authors>Vadim Kreynin</authors>
    <description>
      SystemWrapper is a library that wraps .NET classes for system resources like System.IO.FileInfo, System.Reflection.Assembly, and many other classes so you can easily mock them.
    </description>
  </metadata>
  <files>
    <file src="SystemWrapper\bin\Release\*.dll" target="lib" />
  </files>
</package>

After we updated NuSpec file, we need to repeat step 2 (Build the package).

Step 6: Install the package.

Once again you can install either from Package Manager Console or from Add Library Package Reference dialog.  It’s strait forward to install it from Add Library Package Reference dialog, you just press the Install button.  After the installation, I have SystemWrapper in my Installed packages.  I can easily uninstall it by pressing the Uninstall button.  How easy is that?  Also if I look in Online section, I can see that instead of an Install button there’s a green check mark for my package.

In Package Manager Console I just type Install-Package SystemWrapper at PM> prompt.

PM> Install-Package SystemWrapper

Successfully installed 'SystemWrapper 0.3.5.0'

Successfully added 'SystemWrapper 0.3.5.0' to PackageObjectLibrary

You can uninstall the package by typing Uninstall-Package SystemWrapper.

For more details check out Package Manager Console Commands.

Step 7: Display more information about the package.

When developers browse for packages, they probably would like to more information about a package than just a description.  Adding projectUrl element to NuSpec file will point users to the resource with more details.

Here’s an example for System Wrapper:

<projectUrl>http://systemwrapper.codeplex.com/</projectUrl>

You might also want to add a link to your license terms.  Once again you need to add another field to the NuSpec file.  This time we need to add licenseUrl.  If you don’t want a developer to install your package unless she accepts the license terms, than you need to add requireLicenseAcceptance element. The xml might looks like this:

<licenseUrl>http://systemwrapper.codeplex.com/license</licenseUrl>
<requireLicenseAcceptance>true</requireLicenseAcceptance>

When a user tries to install the package, she will see a dialog similar to the one bellow:

You also can specify your own icon instead of default blue NuGet icon that appears in Add Package Reference dialog .  The element for an icon is iconUrl.  The icon should be a 32×32 pixel PNG file with a transparent background.

<iconUrl>http://mysite.com/32_button_green.png</iconUrl>

The complete NuSpec file might look something like that:

<package>
  <metadata>
    <id>SystemWrapper</id>
    <version>0.3.5.0</version>
    <title>System Wrapper</title>
    <authors>Vadim Kreynin</authors>
    <description>
      SystemWrapper is a library that wraps .NET classes for system resources like System.IO.FileInfo, System.Reflection.Assembly, and many other classes so you can easily mock them.
    </description>
    <projectUrl>http://systemwrapper.codeplex.com/</projectUrl>
    <iconUrl>http://systemwrapper.codeplex.com/32_button_green.png</iconUrl>
    <licenseUrl>http://systemwrapper.codeplex.com/license</licenseUrl>
  </metadata>
  <files>
    <file src="SystemWrapper\bin\Release\*.dll" target="lib" />
  </files>
</package>

 

Summary

I know that I didn’t talk about dependencies or modifying config files at all.  I just try to give a simple example to follow.  I hope that it can help you to get started with NuGet.  Here’s some references I would recommend for you to read:

• Offical NuGet Documentation
• Hosting Your Own Locan and Remote NuGet Feeds – by Phil Haack.
• NuGet CTP 2 changes – by Phil Haack.
• Creating a NuGet Package – by Jeff Kwak.
• Introduction to NuGet – by Scott Hanselman.

MbUnit 3.2 makes it easier to work with Xml

In my previous article I mentioned about upcoming new release of Gallio /  MbUnit.  Feel free to download the Release Candidate and try it for yourself.  In this post I’ll talk about another new feature.

Not everybody like XML but everyone had to work with it. It’s used for many different purposes. Most people use it for configuration like web.config or .csproj / .vbproj. Some people use this format for data, others for communication. I believe that it’s going to be very hard to find a .NET developer that didn’t work with XML. If you do work with XML and you like to unit test your code, than I have good news for you. With new upcoming version 3.2 of MbUnit you are going to get better support to unit test your XML code. The Gallio team gives us three new Assert methods to test XML:

• Assert.Xml.AreEqual
• Assert.Xml.Exists
• Assert.Xml.IsUnique

Assert.Xml.AreEqual

Let start by showing a simple and probably very obvious example:

        [Test]
        public void TestXmlAreEqualWithString()
        {
            const string xmlString =
                "<Books>" +
                "  <Book title='C# in Depth' />" +
                "  <Book title='Learing C#' />" +
                "</Books>";

            Assert.Xml.AreEqual(xmlString, XElement.Load(new StringReader(xmlString)).ToString());
        }

In the example above we’re comparing XML strings.  There’s another overload that instead of strings takes TextReader objects.

        [Test]
        public void TestXmlAreEqualWithTextReader()
        {
            const string xmlString =
                "<Books>" +
                "  <Book title='C# in Depth' />" +
                "  <Book title='Learing C#' />" +
                "</Books>";

            TextReader textReaderXml = new StringReader(xmlString);
            Assert.Xml.AreEqual(
                new StringReader("<Books><Book title='C# in Depth'/><Book title='Learing C#'/></Books>"),
                textReaderXml);
        }

As you can see, the formatting of XML is different, but our test still succeeds since it represents the same XML.

Let’s now make a small test.  We know that XML is case-sensitive  language.  What is going to happen if you we mismatch case?  Let’s make expected value for one of the book title ‘Learning c#’ instead of ‘Learning C#’.

        [Test]
        public void TestXmlAreEqualWithString()
        {
            const string xmlString =
                "<Books>" +
                "  <Book title='C# in Depth' />" +
                "  <Book title='Learing C#' />" +
                "</Books>";

            Assert.Xml.AreEqual(
                "<Books><Book title='C# in Depth'/><Book title='Learing c#'/></Books>",
                XElement.Load(new StringReader(xmlString)).ToString());
        }

After executing this test, we will see the following error that conveniently highlights the problem area:

Wait a second.  But what if in my application I don’t care about case-sensitivity for my data?  Well, in this case guys from the Gallio team provided us with an optional parameter of type XmlOptions.  Therefore, if we add XmlOptions.Loose parameter to our Assert.AreEqual, our test is going to pass.

            Assert.Xml.AreEqual(
                "<Books><Book title='C# in Depth'/><Book title='Learing c#'/></Books>",
                XElement.Load(new StringReader(xmlString)).ToString(), 
                XmlOptions.Loose);

You can find more information on XmlOptions in the Gallio Wiki site.

 

Assert.Xml.Exists

This assertion method checks if an element or an attribute can be found in a specific XML document.

• The first parameter of Assert.Xml.Exists method is an Xml document.   Like in Assert.Xml.AreEqual method you can represent Xml document as a string or a TextReader object. 
• The second parameter is an Xml Path that can be either a string in format “/element[/element]:attribute” or an object that implements IXmlPathLoose interface.
• The third parameter is already familiar to us XmlOptions object.

Let’s look at a specific example where will check if Book element exists. 

        [Test]
        public void TestXmlExistsForElement()
        {
            const string xmlString =
                "<Books>" +
                "  <Book title='C# in Depth' />" +
                "  <Book title='Learing C#' />" +
                "</Books>";

            // Xml Path as a string
            Assert.Xml.Exists(xmlString, "/Books/Book", XmlOptions.Default);
            // Xml Path as a IXmlPathLoose
            Assert.Xml.Exists(xmlString, XmlPath.Element("Books").Element("Book"), XmlOptions.Default);
        }

For completeness let’s show a separate example where we will be looking for title attribute.

        [Test]
        public void TestXmlExistsForElement()
        {
            const string xmlString =
                "<Books>" +
                "  <Book title='C# in Depth' />" +
                "  <Book title='Learing C#' />" +
                "</Books>";

            // Xml Path as a string
            Assert.Xml.Exists(xmlString, "/Books/Book:title", XmlOptions.Default);
            // Xml Path as a IXmlPathLoose
            Assert.Xml.Exists(xmlString, XmlPath.Element("Books").Element("Book").Attribute("title"), XmlOptions.Default);
        }

In case an element or an attribute not found, Gallio will produce an error message similar to the one below:

Assert.Xml.IsUnique

This method takes the same parameters as Assert.Xml.Exists.  Assert.Xml.IsUnique fails if an element is encountered more than once in Xml document.  I expect that you will not utilize this method as much as other two methods.

The following code is going to fail because we have two Book elements in out Xml.

        [Test]
        public void TestXmlIsUnique()
        {
            const string xmlString =
                "<Books>" +
                "  <Book title='C# in Depth' />" +
                "  <Book title='Learing C#' />" +
                "</Books>";

            // Xml Path as a string
            Assert.Xml.IsUnique(xmlString, "/Books/Book", XmlOptions.Default);
            // Xml Path as a IXmlPathLoose
            Assert.Xml.IsUnique(xmlString, XmlPath.Element("Books").Element("Book"), XmlOptions.Default);
        }

Here’s our error message:

Last words.

I hope you find it useful and I didn’t waste mine and your time because my wife and kids never going get this hour back.

 Gallio wiki site is a great place to learn more about XML Assertions.  Gallio / MbUnit is an open source project and they always looking for new contributors.  If you consider joining the project, click here to learn how.

Assert.Count in MbUnit version 3.2

The Gallio team is about to release version 3.2 of Gallio and MbUnit.  If you’re impatient and like to eat your cake hot before it cools down, then download the Release Candidate.  The new version has many new great features.  Click here to see the list of enhancements and here for the bug fixes.

One of the new features is Assert.Count.  It’s impossible to count how many times I wrote code that verifies number of items in the specified collection:

        [Test]
        public void Test()
        {
            var list = new List<int> {2, 3, 5};
            Assert.AreEqual(3, list.Count);
        }

Now with new 3.2 version I can write my code like this:

        [Test]
        public void TestCount()
        {
            var list = new List<int> { 2, 3, 5 };
            Assert.Count(3, list);
        }

I assume that for most people it doesn’t look like a huge improvement and it’s probably not, but it definitely makes code more readable and defines clear the intentions of the specific assertion.

I don’t expect to surprise anybody by telling you that it also works with arrays.

        [Test]
        public void TestArray()
        {
            Assert.Count(3, new[] { 1, 2, 3 });
        }

Actually it works with any object that implements IEnumerable interface even if doesn’t have Count or Length property like CredentialCache class.

        [Test]
        public void TestEnumerable()
        {
            var myCache = new CredentialCache
                         {
                             {
                                 new Uri("http://www.contoso.com/"),
                                 "Basic",
                                 new NetworkCredential("userName", "password")
                             },
                             {
                                 new Uri("http://www.contoso.com/"),
                                 "Digest",
                                 new NetworkCredential("userName", "password", "domain")
                             }
                         };
            Assert.Count(2, myCache);
        }

It even works with string types (of course it does, string also implements IEnumerable).

        [Test]
        public void TestString()
        {
            Assert.Count(5, "Vadim");
        }

How to display your assembly “Add References” dialog.

In Ultimate Software (the company that I work for) we build all the assemblies in the same directory.  Let say it’s C:\Common.  When we need to reference an assembly, we browse to C:\Common directory and select a desired assembly.

I decided to look what we need to do to add our assemblies into .NET tab of “Add Reference” dialog box.  It’s quite simple actually.  All we need to do is to create a registry entry.

First lets assume that we want to reference AssemblyReference.dll that located in C:\Common directory.  It’s probably not going to surprise anybody if I tell you that you’ll not find it in “.NET” tab of Add Reference dialog.

As you can see it’s not there at the moment.  However, if we chose a “Browse” tab and navigate to C:\Common directory will be able to find it.

I just want to point out that adding an assembly to GAC will not add that assembly to the .NET tab’s list.   It’s also not a good practice to install an assembly to the Global Assembly Cache, unless you want to share that assembly with other applications running on that computer. 

Therefore only thing we need to do add our assembly to .NET tab’s list is to create a unique sub-key under

HKLM\SOFTWARE\Microsoft\.NETFramework\.NETMinimumVersion\AssemblyFoldersEx\

If you’re running a 64-bit OS you will need to create it under:

HKLM\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\.NETMinimumVersion\AssemblyFoldersEx\

.NETMinimumVersion is the lowest .NET Framework version from which the assembly can be referenced.  In our example I chose version 2.0.50727 as you can see below.

After creating a new sub-key, we’ll change its default string value to the “C:\Common\” directory path.

After restarting Visual Studio 2010, we can find our AssemblyReference assembly in .NET tab’s list of Add Reference dialog.

In our example we added the sub-key under HKEY_LOCAL_MACHINE node that allows all the users on this system to see AssemblyReference.dll.  If we wanted only the current user to see this assembly, we would create our sub-key under HKEY_CURRENT_USER instead.

Note for VS 2008 and earlier:

For Visual Studio 2008 and earlier you need to add your sub-key under

HKLM\SOFTWARE\Microsoft\.NETFramework\AssemblyFolders\

• How-to from Microsoft:
  For VS 2010
  For VS 2008 and earlier

AssemblyHelpers now works .NET 4 assemblies.

More than two weeks ago I received an email from someone that AssemblyHelper tool doesn’t work with .NET 4 assemblies.

I first mentioned about the tool in Testing internals members with InternalsVisibleTo attribute article.

Here I just want to tell the tool is updated an you can use it against .NET 4 assemblies.  Of course, it still works with assemblies prior version 4.

Feel free to download the updated version.

Visual Studio 2010 RC is out.

Finally VS 2010 RC is out.  It’s available to MSDN subscribers today, February 8th.  Everybody else will be able to download it on February 10th.