Too much column guides in Visual Studio

You installed the Productivity Power Tools extension because you wanted to have nice vertical column guides in Visual Studio, but before you could set one they appeared everywhere?


What’s more you cannot get rid of them, because even if you click exactly the line the Remove Guideline option in the context menu remains disabled?


Here is the solution: turn off not the Column Guides, but instead the Structure Visualizer in the Options dialog:


With that you will lose some tooltip features as well, but at least now it is totally up to you where you want to display column guides.


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Visual Studio: Unable to check out the current file

I’ve received the following error message in Visual Studio right after I’ve tried to add a new service reference:

Unable to check out the current file.  The file may be read-only or locked, or you may need to check the file out manually.

The message was really strange because the Add Service Reference dialog seemed to recognize the service perfectly, and although the project was under source control, we have Git on the server so “check out” did not seem to be the right term here.

The sad truth is that the above error message is completely wrong and the issue has nothing to do with source control. The solution is to click the Advanced button in the Add Service Reference dialog, then click the Add Web Reference button and use the old Add Web Reference dialog to add that particular service to your project even if the URL points to a .svc file.


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Extending your WebAPI documentation

As I already mentioned in a previous post, you can use the Microsoft.AspNet.WebApi.HelpPage NuGet package to generate a human-friendly documentation for your WebAPI directly from your source code. Because the NuGet package installs its full source code, you can customize the generated help pages with a few simple steps.

For example lets assume you designed your API that in case of any error all actions return an error code with the associated error message, and you store the possible errors in a different enum for every action. And of course you want to display these error cases in you API documentation!

Using a custom attribute – which I call here ErrorCodeType – you can connect the error code enum (here MyErrorCodeEnum) to the action on metadata level:


To display this information on the help pages, follow these steps:


1. Create a new class which will describe a single error case. Let’s call it ErrorCodeDescription and place it into the Models folder:

public class ErrorCodeDescription
  public int Code { get; set; }
  public string Message { get; set; }


2. The HelpPageApiModel.cs file contains the view-model which carries the data for the help page. Add a new property to this class which will contain all error cases in a list:

public List<ErrorCodeDescription> ErrorResponses { get; set; }


3. The GenerateApiModel method in the HelpPageConfigurationExtensions.cs file is responsible to build the view-model. You can find the VM in the apiModel variable which has the GenerateApiModel type. Here you can create and call a new custom method which retrieves your custom attribute and builds the ErrorResponses list like this:

private static void GenerateErrorResponses(HelpPageApiModel apiModel)
  ErrorCodeTypeAttribute attribute = apiModel.ApiDescription.ActionDescriptor
  Type enumType = attribute.ErrorCodeEnumType;
  string[] names = Enum.GetNames(attribute.ErrorCodeEnumType);

  foreach (string name in names)
    apiModel.ErrorResponses.Add(new ErrorCodeDescription
      Code = (int) Enum.Parse(enumType, name),
      Message = "TODO"


4. The Views/Help/DisplayTemplates/HelpPageApiModel.cshtml view is responsible for rendering the view-model. Add the following block to the view which delegates the rendering of the ErrorResponses list to the ErrorResponses partial view:

@if (Model.ErrorResponses.Any()) 
  <h3>Error Responses</h3> 
  @Html.DisplayFor(m => m.ErrorResponses, "ErrorResponses") 


5. Finally you have to create the ErrorResponses.cshtml file in the same folder. This partial view will receive a List<ErrorCodeDescription> instance as its @model and it is totally up to you how you want to transform it to a human-friendly HTML page.


At first it may seem too complicated, but in reality the steps are very logical and totally worth the time understanding it.


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Running custom code before and after tests

if you ever wrote a unit test in Visual Studio you probably heard of the [TestClass] and [TestMethod] attributes, that you can use to annotate classes and methods which contain tests. You can use similar attributes to decorate methods, which should run before and after the tests:

Methods decorated with the TestInitialize and TestCleanup attributes are executed before and after each and every test.

Methods decorated with the ClassInitialize and ClassCleanup attributes are executed before the first test and after the last test in the current class.

Methods decorated with the AssemblyInitialize and AssemblyCleanup attributes are executed before the first test and after the last test in the current assembly.

The last two can be particularly useful if you do Continuous Integration.


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Defining a GUID type in XSD

September 30, 2014 Leave a comment

It often happens that an element or an attribute in an XML document contains a GUID value. Because XML documents are useless without the corresponding XSD, it also often happens, that you have to define a GUID in XSD. Although XSD has support for several built-in types, unfortunately GUID is not one of them, and you have to use the classic regex solution:

<xs:schema ...>

  <xs:simpleType name="guid">
    <xs:restriction base="xs:string">
      <xs:pattern value="[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-
[0-9a-fA-F]{4}-[0-9a-fA-F]{12}" />

After this you can refer to your new guid type just like the built-in ones:

<xs:attribute name="id" type="guid" use="required" />

Note that the regex pattern does not have $ and ^  characters in the beginning and in the end, because the pattern should always match the full value.


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HTTPS: Do. Or do not. There is no try.

September 25, 2014 Leave a comment

Last summer I had the chance to visit Bologna, Italy, and I was happy to see that there is free wifi service in the airport. I probably had to be suspicious from the beginning, but it all started to be strange for me, when I saw this “welcome” page in the browser after connecting:


According to the message, the site’s security certificate is “a bit” invalid. Actually it could be more invalid only if it were already revoked.

If you decide to continue you will see this website of the airport:


Really original design. Right, Bologna is not a huge metropolis, but I’m pretty sure it would be easy to find a student of the local university, who could click together a prettier website during a weekend.

This page made me curious and I could quickly find out, that the website has nothing to do with accessing the public internet.

There are many unusual and suspicious aspects here:

  • Certificate
  • IP address
  • Design
  • Phone number collection

This was the moment when I stood up and started to look for Troy Hunt and his Pineapple :)

Most of these concerns of me could be swept away with a single valid SSL certificate. But these invalid certificates do not guarantee anything, except nervous average users and pro users who are worrying about the security of their data.

If you do HTTPS, please do it correctly. Or don’t do it at all. Don’t try.


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JSON or not JSON: that is the question

September 11, 2014 Leave a comment

When you write unit tests for a REST API, you probably want to test whether the given response is in the expected format. For example you want to ensure, that the response string is a valid JSON or not.

You can find a very simple tip on StackOverflow and in other blogs as well: just check whether the first character of the response is a < or { character, because JSON is about Object Notation, right? The problem with this approach is not only that it does not perform a thorough analysis, but also that its basic statement is simply not true. According to, a JSON can also contain only a single value, the specification does not require it to be an object or an array at all:


So I love JSON, 123, true and false are all valid JSON strings.

Unfortunately I could not find a simple IsValidJson method, but I could come up with this solution using Newtonsoft JSON.NET library:

    return true;
catch (JsonReaderException)
    return false;

Is there a better solution?


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Categories: .NET, WebDev Tags: , ,

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