Geert Verhoeven

Adding references - WebSite versus WebApplication

2008-06-03T20:45:00.000+01:00

On my current project I’m creating an ASP.NET site in Visual Studio 2005 SP1.

NOTE: By default, Visual Studio 2005 only allows you to create ASP.NET sites by using the WebSite template but after installing SP1, you can also use the WebApplication template.

For this project we are using the WebSite template since this is the customer’s standard. While developing the application, I noticed that when using the WebSite template, the Add Reference works differently then when using the WebApplication template.

When adding a reference to dll A using the WebSite template, Visual Studio automatically adds a reference to all dll’s that dll A references. This is done to ease the deployment but it can give some unwanted side effects.

To make this clearer, I’ve created a simple solution structure that shows this issue. In the image on the left, you can see 4 projects:

DalLib
BllLib: contains a link to DalLib
WebSite: project using the WebSite template; contains a link to BllLib
WebApplication: project using the WebApplication template; contains a link to BllLib

When you compile this solution, you will notice that the Visual Studio will add the DalLib to the bin folder of the WebSite project. Because of this, you gain access to all the public classes within DalLib from the WebSite. Since I want to avoid direct access from UI to Dal, this is not what I want. When using the WebApplication template, you don’t have this problem.

A possible solution is to make the classes within the DalLib internal and set an InternalsVisible attribute in the AssemblyInfo.cs file of the DalLib (thanks Gert for the tip).

InternalsVisible is a new attribute from.NET 2.0 and is defined in the System.Runtime.CompilerServices namespace.

Vertical split view in Visual Studio 2008

2008-03-26T20:40:00.001+01:00

Just noticed that in Visual Studio 2008 it is possible to change the split screen behavior.

Visual Studio allows you to set the default view (Split, Source or Design) and to choose between a horizontal split and a vertical split. Especially this last option is very handy when you have a widescreen monitor.

To change the settings, go to Tools\Options\Html Designer

Quiz 1: Generic class with static fields

2008-02-08T15:46:00.001+01:00

In the following piece of code you can see 2 instantiations of a generic class. What is the output of this console application?

using System;
using System.Collections.Generic;


namespace DEMO
{
    class Program
    {
        static void Main(string[] args)
        {
            GenClass<int> x = new GenClass<int>();
            GenClass<double> y = new GenClass<double>();

            x.Add(1);
            y.Add(2);

            Console.WriteLine(y.Get(0));
        }

        public class GenClass<T>
        {
            public static List<T> list = new List<T>();

            public void Add(T x)
            {
                list.Add(x);
            }

            public string Get(int index)
            {
                return list[index].ToString();
            }
        }
    }
}

I'll post the response in a comment.

Anonymous types and equality

2008-01-27T16:23:00.001+01:00

Introduction to anonymous types

Most of the applications created in .NET contain classes defined by the developer. There are two types of classes. First you have the type that only contains fields and is used to transfer data, then you have a second type that also provides functionality to the application by implementing logic in methods, events, ... .

As from the .NET 3.5 framework, Microsoft has added anonymous types. Anonymous types that are created dynamically at compile time.

With anonymous types, the developer no longer has to define the type structure. Sounds great doesn't it. Although there are some limitations. For example, anonymous types can only be used as local variables. This means that the definition of a type is only valid within a single method. It is possible to pass instances of an anonymous type between methods but then the parameter of the receiving method should be of type object which is mostly not a best practice and difficult to work with.

This limits the use of anonymous types. As for most of the .NET 3.5 language enhancements, anonymous types are implemented to be able to support Linq.

To create an anonymous type, you need to use the var keyword in combination with the new object initialization syntax (also one of the .NET 3.5 language enhancements).

Sample

In the following sample, I'll show you how to create an anonymous type as well as how an anonymous type behaves when using equality methods.

using System;

class Program
{
   static void Main(string[] args)
   {
      // Creation of an anonymous type
      var p1 = new
      {
         FirstName = "Geert",
         LastName = "Verhoeven",
         Age = 26
      };

      // Error: 
      // Property or indexer 'AnonymousType#1.Age' 
      // cannot be assigned to -- it is read only    
      // p1.Age = 27;

      Console.WriteLine(p1.ToString());

      var p2 = new
      {
         FirstName = "Geert",
         LastName = "Verhoeven",
         Age = 26
      };      

      var p3 = p1;
      
      // Comparison based on the == method.
      Console.WriteLine("person1 == person2: {0}",
          p1 == p2);

      // Comparison based on the equals method.
      Console.WriteLine("person1.Equals(person2): {0}",
          p1.Equals(p2));

      // Comparison based on the == method.
      Console.WriteLine("person1 == person3: {0}",
          p1 == p3);
   }
}

Output:

There are some important things to note when looking at this output.

At first, if you look at the result of the ToString() method, you can see that the behavior is different then with normal types. By default, when not overridden, the ToString() method returns the types fullname. This means that an anonymous type has an override for the ToString() method.

Secondly, the Equals method behaves differently as well. When not overridden, the Equals method checks whether 2 objects refer to the same memory object. This means that the anonymous type for the Equals method as well.

The == operator still acts the same as with normal objects. From these results we can conclude that when using the Equals method, an anonymous types acts like a value type. When using the == operator, the anonymous type acts like a reference type.

Now how is this possible since we didn't write any code for these overrides? When opening the assembly with a tool like Reflector, we can see the structure of the generated anonymous type and see that the compiler did this for us.

internal sealed class <>f__AnonymousType0<<FirstName>j__TPar, <LastName>j__TPar, <Age>j__TPar>
{
    private readonly <Age>j__TPar <Age>i__Field;
    private readonly <FirstName>j__TPar <FirstName>i__Field;
    private readonly <LastName>j__TPar <LastName>i__Field;

    public <>f__AnonymousType0(<FirstName>j__TPar FirstName, <LastName>j__TPar LastName, <Age>j__TPar Age);
    public override bool Equals(object value);
    public override int GetHashCode();
    public override string ToString();

    public <Age>j__TPar Age { get; }
    public <FirstName>j__TPar FirstName { get; }
    public <LastName>j__TPar LastName { get; }
}

Strange behavior with extension methods

2008-01-17T23:17:00.001+01:00

In a previous post, I already explained what extension methods are and how they work. While doing some tests, I noticed a strange behavior which I will explain in this post.

The order in which .NET searches for the method to be executed is as follow:

Instance methods of the class
Static methods within the class
Extension methods specified for the class

Because the static methods have a higher priority then the extension methods, this can give strange behavior.

In the following sample, the goal is to create an extension method that enables making comparisons on DateTime objects on different levels. The comparison level allows you for example to only compare until the month and not use the day/time while doing the comparison.

using System;
using System.Collections.Generic;


class Program
{
   static void Main(string[] args)
{
   DateTime d1 = new DateTime(2008, 1, 1);
   DateTime d2 = new DateTime(2008, 1, 10);

      // Compile time error:
      // Member 'object.Equals(object, object)'
      // cannot be accessed with an instance
      // reference; qualify it with a type
      // name instead 
      d1.Equals(d2, DateComparisonLevel.Month);
}
}

public enum DateComparisonLevel
{
Year,
Month
}

public static class MyUtils
{
   public static bool Equals(this DateTime orgDate,
     DateTime compDate, DateComparisonLevel level)
{
      switch (level)
   {
         case DateComparisonLevel.Year:
            return orgDate.Date.Equals(
                      new DateTime(
                       compDate.Year,
                       orgDate.Month,
                       orgDate.Day));

         case DateComparisonLevel.Month:
            return orgDate.Date.Equals(
                      new DateTime(
                       compDate.Year,
                       compDate.Month,
                       orgDate.Day));
   }

      return false;
}
}

When trying to compile this code, you will receive a compile time error on the following line:

d1.Equals(d2, DateComparisonLevel.Month);

Error:

Member 'object.Equals(object, object)' cannot be accessed with an instance reference; qualify it with a type name instead.

This is because DateTime derives from System.Object. Since System.Object contains a method with definition

public static bool Equals(object objA, object objB);

the compiler takes this method in case of the extension method. Since the method of the System.Object class is a static method, it can not be called from an instance of an object. The only way to solve this is to rename the Equals method in the code. This way, the Object.Equals method will no longer interfer.

Microsoft considers this as a bug.

Introduction to extension methods

2008-01-17T23:03:00.001+01:00

What it is

Extension methods allow you to extend an existing type without needing access to the type's code. Before .NET 3.5, this wasn't possible without having access to the type's code or without using the System.Reflection.Emit namespace.

In short, extension methods are static methods that can be executed by instances of the extended object. Behind the scenes, the call to the extension method is nothing more then a call to a static method.

Behind the scenes, extension methods are marked with the System.Runtime.CompilerServices.ExtensionAttribute which is located in the Systme.Core.dll. So a reference to this DLL is necessary in order to create extension methods.

When to use

If you have a class that you want to extend but you don't have the source code, extension methods can be an answer. Also when extending a class with extension methods, you don't have the risk of breaking existing code which you can have when changing the type's definition.

Simple sample

In this sample, I'm adding a method IsWeekend to the DateTime type which will return a boolean to indicate whether a given date falls in the weekend or not.

using System;


class Program
{
  static void Main(string[] args)
  {
      // Tuesday
        DateTime d1 = new DateTime(2008, 1, 1);

      // Saturday
        DateTime d2 = new DateTime(2008, 1, 5); 

      Console.WriteLine("{0:d} is weekend: {1}",
                          d1, d1.IsWeekend());
      Console.WriteLine("{0:d} is weekend: {1}",
                          d2, d2.IsWeekend());

  }
}

public static class MyUtils
{
  public static bool IsWeekend(this DateTime date)
  {
      return (date.DayOfWeek == DayOfWeek.Saturday
        || date.DayOfWeek == DayOfWeek.Sunday);
  }
}

Extension methods must be created within a static class (each method within the class must be static as well). The first parameter of the method is marked with the this keyword and indicates the type to which the method should be applied (in this case DateTime). It is possible to add multiple parameters. Only the parameters after the first parameter, should be provided when using the method.

When you've implemented an extension method for a specific type, you will see that it is showed by intellisense with a specific icon.

It is possible to create a separate assembly with all your extension methods. Note that you need to add using statements for the namespaces where the extension methods are located.

Installation issues with Windows Live Writer when using a corporate proxy server

2007-12-26T11:03:00.000+01:00

When installing Windows Live Writer on a machine that is connected via a corporate proxy to the internet can be a real pain. Since the installer is downloading .exe files, the files can be blocked.

Today I've found this blog post which shows a way to install the Windows Live tools on a corporate machine.

Visual Studio 2008 available

2007-11-21T08:40:00.000+01:00

For those of you who didn't know yet, Visual Studio 2008 is available since a few days.

MSDN Subscribers can download the full version where as others can download a 90-day trial.
http://msdn2.microsoft.com/en-us/vstudio/aa700831.aspx

Yesterday I've been able to install it on a Windows XP SP2 machine without any problems.

NOTE: When opening a solution or project file created in a previous version, an upgrade wizard will be launched. If you upgrade your project, you can not open it any more with the previous version.

Firefox's "functionality" to show your saved passwords in clear text

2007-10-04T17:52:00.000+01:00

While making a joke about Firefox, I noticed that a lot of people don't know that Firefox has a functionality that makes it possible to show your saved passwords. This can be handy for you whenever you forget one but also very handy for someone who uses your pc with the same account.

Before judging, I must say this password manager can be disabled or secured but by default it is enabled without security.

The problem

If you browse to a site that requires you to sign in with name and password (for example http://www.gmail.com/), Firefox will give you the possibility to save your password as in IE.

However, with Firefox it is possible to actually see the passwords in clear text. This is how to do it:

Go to Tools\Options and select the Security tab

Click “Show Passwords”
This will open a new screen and show you the sites and accounts; not the passwords.

Click “Show Passwords” and choose “Yes” in the warning dialog (don’t do this when other people are standing next to you)

This will add an additional column in the table which shows your passwords in clear text.

I think you understand that this can be dangerous!

The solution

As mentioned before, there is a way to disable (by unchecking the "Remember passwords for this site" option) or secure this.

To secure this, Firefox uses a master passwords to access your saved passwords. You can do this by checking the “Use a master password” in the “Security” tab from the Options window. Firefox will ask you to enter a new password.

The master password needs to be entered each time you want Firefox to use your saved passwords or to view the list of passwords.

Implementing the IEquatable interface properly

2007-09-21T15:44:00.001+01:00

I've posted an article on CodeProject that illustrates why it is important to override the Object.Equals method when implementing the IEquatable interface.

The article first explains when to use the IEquatable and how to do a proper implementation.

If you have any questions or comments, feel free to post them.

Passed the 70-526 exam

2007-09-10T18:40:00.000+01:00

Two weeks ago I've passed the MCTS exam for Windows Application (070-526). To study this exam I've used the MS PRESS book which helped me very good. The book explains the topics very well and contains good exercises.

Most of the questions where more or less discussed in the book. I did get a lot of questions on deployment and printing.

After taking 2 weeks of I'm back on track for the next exam 70-548 (MCPD Windows Applications).

How Windows Vista fills your disk

2007-08-20T20:47:00.001+01:00

Recently I reinstalled my PC and installed Windows Vista on it. After using it for a month, I noticed that the free disk space was becoming very limited. In explorer the disk property showed me that I used 46GB but when I selected all my folders and retrieved the size, it was only 21GB.

So where did that 25GB go? Aparently it is the system restore utility (which uses shadow copies) that is happily using my free disk space. Especially on a laptop with limited disk space this is not funny. Opposed to Windows XP, Vista doesn't provide a graphical utility to manage the system restore memory settings. Although, there is a way to change these settings.

If you open a command prompt and type vssadmin list shadowstorage, you can see the used space.

To change the settings, you need to use the vssadmin resize shadowstorage /for=[disk_drive]: /on=[disk_drive]: /maxsize=[max_size]. The sample below sets these settings on my machine to a maximum of 1GB:

vssadmin resize shadowstorage /for=c: /on=c: /maxsize=1GB

References:

http://blogs.technet.com/filecab/archive/2006/11/16/identifying-how-much-disk-space-is-used-for-restore-points-in-windows-vista.aspx

"Upgrade patch can not be installed ..." while installing Visual Studio SP1 for Vista

2007-08-06T20:37:00.001+01:00

To be able to use Visual Studio 2005 on a Windows Vista machine, you need to install a special service pack: (Visual Studio 2005 Service Pack 1 Update for Windows Vista).

When starting the installation I received the following error:

The upgrade patch cannot be installed by the Windows Installer service because the program to be upgraded may be missing, or the upgrade patch may update a different version of the program. Verify that the program to be upgraded exists on your computer and that you have the correct upgrade patch.

The service pack is searching for specific components that are not available. These components ship with the standard SP1. So before installing the Vista specific service pack, you need to install the standard SP1.

Reporting Services on a Vista machine

2007-08-06T20:25:00.001+01:00

Since a while I have reinstalled my test pc to be able to experiment with the new Windows operating system. When trying to install Reporting Services 2005, the setup gave me the following warning:

IIS Feature Requirement ...

It seems that Reporting Services can't find IIS although it is installed on my PC (note Vista has IIS 7).

After googling a while, I found the following article: http://support.microsoft.com/kb/920201/en-us. Apparently it is necessary to install specific IIS 7 components in order to be able to install Reporting Services on a Vista machine.

Passed the 70-536 exam

2007-07-28T09:22:00.001+01:00

Yesterday I've passed the 70-536 exam (TS: Microsoft .NET Framework 2.0—Application Development Foundation).

To study the exam I've used the Microsoft Training Kit. The book is easy to read and has good practices. It covers all the topics discussed in the exam. Sometimes not in so much details but that is normal I guess.

The next exam that I'm going to do is 70-526 (TS: Microsoft .NET Framework 2.0 – Windows-Based Client Development). I could have choosen for the upgrade exam (MCSD to MCPD) but I prefer to do the exams one by one. This gives me an extra review on things that I don't use that often.

Windows Live Writer: creating blog entries in just a few seconds

2007-07-25T19:10:00.001+01:00

In a previous post I've mentioned the possibilities of Word 2007 to create new blog entries. A colleague of me informed me about a tool names Windows Live Writer which is a tool created by Microsoft to create blog entries. After testing it for a while, I'm now using Live Writer as my primary blogging tool. You can download it here (currently in Beta).

Especially in combination with the free SyntaxColor4Writer plug-in, creating posts that contains code is no longer a time consuming job. The plug-in allows you to add code to your blog without having to worry about the colors and formatting.

Currently it supports 20 different formats including C#, VB.NET, HTML, XML, SQL, ...

Create a function that returns a table

2007-07-25T18:17:00.000+01:00

In SQL Server it is easy to create a function that returns a table when used in the from clause. In Oracle this is not as easy as it seems but since my current client uses Oracle, I was forced to find a solution so here it is.

To create a function that returns a table in Oracle you need to follow a few steps:

Create a type that corresponds to a single record
Create a type that corresponds to a table and that has the previously declared type as recordtype
Create the function

To use the function, you need to include it in the TABLE() function.

Here is an example on how to do it:

First I create a simple table that will be used for the sample.

-- Create a dummy table to show how it works.
-- The table contains a hierarchy between boss 
-- and employee.
CREATE TABLE employee
(
  emp_id       NUMBER(10),
  full_name    VARCHAR2(50),
  emp_boss_id  NUMBER(10)
);

-- Insert dummy data:
INSERT INTO employee VALUES (1, 'Geert Verhoeven', null);
INSERT INTO employee VALUES (2, 'Ford Parker', null);
INSERT INTO employee VALUES (3, 'Al Bino', 1);
INSERT INTO employee VALUES (4, 'April May', 1);
INSERT INTO employee VALUES (5, 'Abbie Birthday', 3);
INSERT INTO employee VALUES (6, 'Gene E. Yuss', 3);
INSERT INTO employee VALUES (7, 'Juana Bea', 3);
INSERT INTO employee VALUES (8, 'Willie Maykit', 4);
INSERT INTO employee VALUES (9, 'Zoltan Pepper', 4);
INSERT INTO employee VALUES (10, 'Scott Shawn DeRocks', 4);
COMMIT;

Then I create the types needed to be able to return a table

-- Create a type that corresponds to a row that you want to have returned.
CREATE TYPE ind_employee AS OBJECT (emp_id NUMBER(10), full_name  VARCHAR2(50));
--
 Create a type that corresponds to a table of rows with the specified type.
CREATE TYPE ind_employee_table AS TABLE OF ind_employee;

After this is done, you can create a function that returns a table.

-- Create the function.
CREATE OR REPLACE FUNCTION FN_GET_EMPLOYEE_DESCENDANTS (
    pin_emp_id IN NUMBER
) RETURN ind_employee_table PIPELINED 
IS  
    
TYPE t_ref_cursor IS REF CURSOR;    
lc_employees        t_ref_cursor;
lr_out_rec          ind_employee := ind_employee(NULL, NULL);
    
BEGIN
    OPEN lc_employees FOR 
        -- The connect by prior handles the hierarchy.
        SELECT 
            emp_id,
            full_name 
        FROM employee    
        START WITH emp_id = pin_emp_id
        CONNECT BY PRIOR emp_id = emp_boss_id;
  
        LOOP
            FETCH lc_employees 
            INTO 
                lr_out_rec.emp_id,    
                lr_out_rec.full_name;
            
            EXIT WHEN lc_employees%NOTFOUND;
            PIPE ROW(lr_out_rec);
        END LOOP;
    CLOSE lc_employees;
    RETURN;
END;

REMARKS: The PIPELINED command and PIPE ROW() method, work together to make sure that each row is returned to the caller immediately after it is processed. This helps to avoid having big objects in memory.

To use the function, you need to use the TABLE() function.

-- Sample query:
SELECT * FROM TABLE(FN_GET_EMPLOYEE_DESCENDANTS(1));

This gives the following results:

EMP_ID    FULL_NAME

1    Geert Verhoeven
3    Al Bino
5    Abbie Birthday
6    Gene E. Yuss
7    Juana Bea
4    April May
8    Willie Maykit
9    Zoltan Pepper
10    Scott Shawn DeRocks

How (not) to create a deadlock with the Thread.Join() method

2007-07-19T18:05:00.001+01:00

In one of my projects I needed to be able to execute multiple tasks at the same time and show the results when all the tasks were finished.

The tasks included updating of the user interface. Since you cannot update a control on the user interface from a thread different than the thread that owns the control, you need to use the Control.Invoke method.

Control.Invoke(delegate method) executes the specified delegate on the thread that owns the control. So this way, you can have a second thread make a call to the main thread to update the user interface. So far so good.

The goal was to load multiple datasets in different threads and call a Control.Invoke for each dataset to bind it to a control on the form. After all the threads were finished, I wanted to show the form to the user.

To be able to check that all the threads were finished, I used the Thread.Join() method. This method blocks the main method until the thread finishes. If you create a loop that loops through all the threads you started and call Thread.Join() you are sure that all threads have finished.

The issue with this is that Thread.Join() blocks the main thread. So it also blocks the calls made via Control.Invoke. This is why you can't use Thread.Join() in combination with Control.Invoke. Pretty logic but if you don't realize what is going wrong, you can spent quite some time on it.

References:

Blogging with Office 2007

2007-07-17T11:10:00.001+01:00

Since a few days I'm using Word 2007 to create new blog entries. I've tried several utilities to add new blog entries but was always struggling with the layout. After doing a few tests, I'm very pleased with Word 2007. The only pity is that since I'm using Blogger, I can't upload images and don't have the possibility to add tags (Categories).

Here is a link on how to get it started http://spsfactory.blogspot.com/2007/03/blogger-is-integrated-in-microsoft.html.

Add a new code group based on a .snk file by using the caspol command line

2007-07-09T20:31:00.001+01:00

For one of my projects, I needed to be able to give the FullTrust permission to my smart client applications. Since all the applications created at the client are signed using the same strong name key, I've used this to set up the security requirements.

Normally I would use the ".NET Framework 2.0 Configuration" but not all the user's have the .NET Framework SDK installed (which includes the configuration tool), I used the caspol.exe command line to set the security permissions.

Since it took me quiet some time to get all the parameters right, I thought to give you a head start by posting the commands.

Steps to follow to add a new code group that gives fulltrust to all applications signed by a given snk file. In order to add the strong name to the security policies, you either need to have a signed dll/exe or the snk file. The below sample uses an .snk file.

Extract the public key from the .snk file (in this case Sample.snk) by using the sn.exe tool:

sn -p sample.snk sample.pk

Now you need to have the hex value of the public key (saved in sample.pk). Since notepad doesn't support the format of the .pk file, you need to have a hex editor to open it. I used the free HxD tool which has all the features you need (http://mh-nexus.de/hxd/).

Open HxD.exeOpen the sample.pk file and copy the hex value.

3. The following command creates the new key in the machine security policy:

caspol -machine -addgroup 1 -strong -hex "0024000004800000940000000602000000240000525341310004000001000100DDEEAD8B27321D3FB0E872FABDFA62627CCA03864AF3F7A19C6D978788F5DCD89BEFD1B897BAC5C74253091FB6747E2723D5239B802F074B1AC930A9C187D52FCF3ED65AF467F4F656F392CF5E6E2FF69071C398EA931B2EB862F6CE832350B24A6524F06F9F5F630A2B00B30F59A87BC847989D2D09DDD7A49BE92FE2EFB5B2" -noname -noversion FullTrust -name "Code Group Name" -description "Code Group Description" -exclusive on

The hex key can not contain any spaces or carriage returns so you need to remove them from the copied result.

References:

Problems when signing my ClickOnce application

2007-07-06T18:21:00.000+01:00

When I tried to sign my ClickOnce application, I received the following error:

Unable to find manifest signing certificate in the certificate store.

I’ve noticed that even after removing the sign option in the project properties page, the .csproj file (opened with notepad) still contained parameters indicating that the application needed to be signed.

<SignManifests>true<SignManifests>
<ManifestCertificateThumbprint>ACBE668D16D794DA9E35301D49C834864C4D9C2A<ManifestCertificateThumbprint>
<ManifestKeyFile>GuiWinApp_TemporaryKey.pfx<ManifestKeyFile>

After removing these lines of code and reselecting the .snk file in the property pages, everything worked fine.

Creating and using code snippets

2007-04-05T19:42:00.000+01:00

One of the features that I really appreciate in Visual Studio 2005 is "code snippets". Code snippets help you to speed up the development by giving you shortcuts to frequently used code.

For example if you want to create a for loop, you simply type for and press the "TAB" button twice.

Visual Studio will then automatically generate the code for you as you can see below.

By using the tab key, you can navigate to the marked words which enables to specify your own names.

That's not all. The nicest thing about code snippets is that you can create your own code snippets.

In the following example, I'll show you how.

Create a new file cend.snippet within Visual Studio 2005 and save it under the ...\My Documents\Visual Studio 2005\Code Snippets\Visual C#\My Code Snippets folder.
Copy the following code in the file, I'll explain the code in a minute:

<?xml version="1.0" encoding="utf-8" ?> <CodeSnippets xmlns="http://schemas.microsoft.com/VisualStudio/2005/CodeSnippet"> <CodeSnippet Format="1.0"> <Header> <Shortcut>cend</Shortcut> <Title>End console</Title> <Description>Code snippet for ending a console application</Description> </Header> <Snippet> <Declarations> <Literal> <ID>EndMessage</ID> <Default>Press any key to continue ... </Default> </Literal> </Declarations> <Code Language="CSharp"> <![CDATA[ Console.WriteLine("$EndMessage$"); Console.ReadLine(); ]]> </Code> </Snippet> </CodeSnippet> </CodeSnippets>
Save the file and open a C# application. In one of the .cs files, type cend which will popup the intellisense menu.

When you press the "TAB" key twice, the following code will be generated:
How does it work:
The second line in the snippet file informs Visual Studio to use an xsd to help you by providing intellisense (the xsd is located in C:\Program Files\Microsoft Visual Studio 8\Xml\Schemas\1033\snippetformat.xsd depending on where you installed VS):

<CodeSnippets xmlns="http://schemas.microsoft.com/VisualStudio/2005/CodeSnippet">
The shortcut contains the shortcut that you can use to reference to your code snippet. You can also reference the code snippets via the menu or via the Ctrl+K, Ctrl+X combination.
A literal is a variable that can be used within your code snippet. When using the code snippet, each literal is a placeholder for user input. You can add a default value as done in the sample.
Within the code element, comes the real code snippet. It is embedded in a CDATA element to be able to include special elements in the xml document.
It is possible to create multiple snippets (1 snippet per file).

Finally passed the 70-300 exam

2007-03-18T20:07:00.000+01:00

The last weeks it has been very quited on my blog since I've been busy with studying for the 070-300 exam. This is one of the exams that I was planning for a long time but never had the time to do it. So last friday I finally passed it.

I've used the MS PRESS book (Analyzing Requirements and Defining Microsoft .NET Solution Architectures, Exam 70-300) to study for the exam. The book is pretty good but I found that the MOC 2710 was more related to the exam.

Could not load file or assembly after installing LINQ May 2006 CTP

2007-03-01T20:05:00.000+01:00

When working with the class designer in Visual Studio 2005 I received the following error:

Could not load file or assembly 'Microsoft.VisualStudio.CSharp.Services.Language, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

I remembered that I installed the "Microsoft Visual Studio Code Name “Orcas” Language-Integrated Query, May 2006 Community Technology Preview" the day before.

After uninstalling the Linq CTP, everything worked fine again. I didn't find a real solution yet but since it is a CTP version I don't bother too much.

Get the value of the identity column after inserting a record

2007-02-22T20:06:00.000+01:00

Aparently there are still a lot of people who are having problems when inserting rows in a table that has an identity field. Sometimes you need to have the id of the record you just inserted to be able to use it afterwards.

Yesterday I saw someone doing a SELECT MAX(id) FROM MyTable to be able to get the maximum id and then raise it by 1. This gives 2 issues:

what if someone else has added a row after you selected the maximum value?
what if the identity increment is not 1?

In SQL Server there is a function SCOPE_IDENTITY() that returns the last used identity within the scope of the statement. If you add this to the end of your statement, you can return the value of the identity column.

Here is a sample that shows you how to do it (NOTE the end of the select statement):

static void Main(string[] args)
{
   int identity = -1;
   string connectionString = "Data Source=LP51; Initial Catalog=Northwind; User Id=sa; Password=P@ssw0rd;";
   string sql = "INSERT INTO Employees (LastName, FirstName) VALUES (@LastName, @FirstName) SELECT SCOPE_IDENTITY()";
   SqlConnection conn = new SqlConnection(connectionString);
   SqlCommand cmd = new SqlCommand(sql, conn);
   cmd.Parameters.AddWithValue("@LastName", "Verhoeven");
   cmd.Parameters.AddWithValue("@FirstName", "Geert");

   try
   {
      conn.Open();
      identity = int.Parse(cmd.ExecuteScalar().ToString());
   }
   catch
   {
      // implement exception handling here
   }
   finally
   {
      conn.Dispose();
      cmd.Dispose();
   }

   Console.WriteLine("The identity is {0}", identity);
   Console.WriteLine("Press any key to continue ...");
   Console.ReadLine();
}