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Passing Anonymous Types with Dynamic Lists October 1, 2013

Posted by codinglifestyle in C#, CodeProject, Javascript.
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Recently I was rewriting a function with a large method signature which took several arrays as parameters.  As you might guess, the index across these arrays was assumed to be the same which is error-prone.  I thought we should really encapsulate all this information in to a class or struct and pass in a single list instead.  Then I stopped myself as there was no use for this class beyond this one-time call to another function.

Then I thought, I know, I could use an anonymous type instead.

var datum = new { a = myData.a, b = myData.b, /* c, d, ..., */ z = myData.z };

This seems like a reasonable approach and exactly what throw-away anonymous types are for.  Then I tried to add this to a list.  Hmm, with a little creativity I was able to overcome this… except it only worked within the scope of the same function.  Well, I could have passed a list of objects, but what would I cast them to?

I really thought I’d have to cave in and just create the new class but then there was one option I hadn’t considered: dynamic.  Like JavaScript, this frees you from the restriction of static typing which was inhibiting a simple notion to pass a list of anonymous types to another function.  Now our list definition looks like this:

var data = new List<dynamic>();

Now this means I could really add in anything and its evaluation will be resolved at runtime.  So we’re finally free to use our anonymous class however we want.  We could even code access to properties which we aren’t supplying and code will compile (however you’ll get a nasty surprise at runtime).

protected void Bob()
{
    List<dynamic> data = new List<dynamic>();

    //
    //Assume lots of processing to build up all these arguments
    //
    data.Add(new { a = 1, b = "test" });

    Fred(data);
}

private void Fred(List<dynamic> data)
{
    //Fred processing logic
    foreach (var datum in data)
    {
        Trace.WriteLine(String.Format("{0}: {1}", datum.a, datum.b));
    }
}

The more evolved my client coding becomes the more restraining statically typed languages can feel.  With the dynamic keyword C# is one step ahead of me allowing a future of amazing code determined by an unlimited number of factors at runtime.

Visual Studio 2008 JumpStart December 18, 2007

Posted by codinglifestyle in ASP.NET, C#, Javascript, jQuery, linq.
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Yesterday I attended the Visual Studio 2008 Jumpstart at Microsoft in Dublin.  This was a one-day course, presented by David Ryan, introducing some of the new features in C# 3.0 and VS2008.

 

I approach every release with excitement and trepidation.  There are some fantastic new features like JavaScript debugging, nested MasterPages, improved IDE for both coding and web design, and multi-target runtime support.  With multi-targeting support we can use VS2008 to continue to code or support .NET 2.  If you open a VS2005 project, you will be prompted to upgrade your project even if you continue to use .NET 2.  I asked was there any risk associated with this for those who need to continue to support .NET 2 and was told only the SLN file is changed.  So theoretically, there is no reason to keep VS2005 installed!  Do you believe it??  If only we could get rid of VS2003 as well.

 

Now, the reason I also approach each release with trepidation is because you know there is going to be some big, new, ghastly feature which will be force-feed to us like geese in a pâté factory.  This time that feature in LINQ.  Open wide because there is a big push behind LINQ and you’ll notice a using System.Linq statement in every new class (which is a real pain if you change target framework back to .NET 2).  But first, let’s review some of the changes made to C#:

 

  • Anonymous types
    • var dt = DateTime.Today;
    • Anything can be assigned to a var, but once it’s assigned its strongly typed and that type can’t be changed.  So I can’t reuse local variable dt and assign string “Hello” like I could with object.
  • Automatic Properties
    • This:

      private int m_nID;

         public int ID

         {

             get

             {

                 return m_nID;

             }

             set

             {

                 m_nID = value;

             }

         }

 

  •  
    • becomes this:

public int ID { get; set; }

 

  •  
    • The problem is in practice I prefer to use the private variables in code leaving properties for external access only.  Many times the get/set is doing something interesting, like reading the value from a cache or performing some complex operation.  We don’t necessarily want/need this code to execute every time it is accessed from within the class so I use the private variable.  Automatic Properties has us using the public property directly everywhere in the class.  So, personally, this will cause inconsistency in my coding style.
    • You can also specify the get as public but keep the set to just be accessible from within the class like this:

public int ID { get; private set; }

 

  • Object initalizers
    • Ever have to instantiate your own class and have to initialize it with a dozen properties?  Do you add 13 lines of code or go overload the constructor?  Now you don’t have to, imagine a simple Person class with 3 properties:

Person person = new Person { FirstName=“Chris”, LastName=“Green”, Age=33 };

 

  •  
    • Only initialize what you properties you want:

Person person2 = new Person { FirstName = “Chris”, LastName = “Green” };

 

  • Collection initalizers

List<Person> people = new List<Person>

         {

new Person { FirstName = “Chris”, LastName = “Green”, Age = 33 },

new Person { FirstName = “Bill”, LastName = “Bob”, Age = 46 },

new Person { FirstName = “Foo”, LastName = “Bar”, Age = 26 }

         };

 

  • Extension methods
    • This is a way of adding new inherent functionality to existing classes.  The objective is to add a new method to the DateTime type called LastDay() which will return the last day of the given date’s month.

public static class DateTimeUtils

{

        public static int LastDay (this DateTime dt)

        {

            return DateTime.DaysInMonth(dt.Year, dt.Month);

        }

}

 

  •  
    • Notice the this before the first parameter argument.  This tells the compiler that this is an extension method for the DateTime type.  We can now use this method as if it was built in to the DateTime class:
      • int nLastDay = dt.LastDay();
  • Lambda expressions
    • Too lazy or couldn’t be arsed to write a small 2 line function?  This is for you:

Func<string, bool> CheckName = sName => sName == “Bob”;

bool bBob = CheckName(person.FirstName);

Func<int, int> Square = x => x * x;

int nSquare = Square(5);

 

The fact is there’s an ulterior reason var, Lamda expressions, and many of above additions have been added to C# 3.0.  C# had been bent in order to accommodate LINQ.  LINQ allows you to perform queries on objects, DataSets, XML, and databases.  It’s interesting in that it offers an independent layer of abstraction for performing these types of operations.  This has actually occurred to me before when looking at data layers chock full of embedded SQL not being particularly ideal.  LINQ offers a generic and powerful alternative.  Let’s take a look at a simple example based on the people collection from above:

 

var matches = from person in people

              where person.FirstName == “Bob”

              select person;

 

The first thing that caught my attention was the select was last.  One reason they likely did this was to force us to state what we were querying first (the from clause) so that Intellisense could kick-in for the rest of the expression.  Notice person.FirstName was fully supported by Intellisense so the Person class was automatically inferred from the people collection.

 

You can create objects on-the-go from your expression.  For example:

 

var matches = from employee in people

              where employee.FirstName == “Bob”

              select new Person(employee.FirstName, employee.LastName);

 

 

Notice how var is inherently handy here (but bad practice for nearly everything else) as our LINQ expression returns System.Collections.Generic.IEnumerable.  Lambda expressions as well play a key part in LINQ:

 

var matchesBob = people.Select(CheckName => CheckName.LastName == “Bob”);

 

matchesBob.ToArray()

{bool[3]}

    [0]: false

    [1]: true

    [2]: false

 

var matchesInitials = people.Select(ChopName => ChopName.FirstName.Remove(1) + ChopName.LastName.Remove(1));

 

matchesInitials.ToArray()

{string[3]}

    [0]: “CG”

    [1]: “BB”

    [2]: “FB”

 

There is so much more to LINQ that I won’t attempt to cover any more.  Rest assured you will hear much more about LINQ in the months to come (fatten up those livers).  One thing is obvious, C# took a heavy hit in order to support it.  Let’s hope it’s worth it as every release we lean more and more towards VB.  A colleague recently remarked, “C# is all VB under the covers anyhow”.  He might be right.

 

Some other interesting new additions:

  • XElement – for anyone who has programmatically built XML before you will appreciate this quicker alternative
  • ASP.NET ListView – the singular new control this release.  Its basically a Repeater but with design-time support
  • Script Manager Proxy – typically the Ajax ScriptManager will be placed in the MasterPage.  When the content page needs to access the ScriptManager a ScriptManagerProxy can be used to get around the restriction of only one ScriptManager allowed per page.
  • Javascript enhancements – built-in libraries which extend string, add StringBuilder, and a number of other enhancements to make writing JavaScript more .NET-like
  • CLR Add-In Framework: essentially a pattern for loading modules (only from a specified directory) vs. using reflection, iterating classes for a specified type, and using the activator to instantiate the object
  • Transparent Intellisense: In VS2005 Intellisense went in to hyperdrive and our tab keys have never been the same.  However, I often found myself cursing it as it often got in the way.  So when VS is being too helpful and you can’t see what you’re doing press CTRL rather than ESC to turn Intellisense transparent.
  • Right-click the code and you will see an Organize Using menu below Refactor.  Here is a feature I’ve often dreamed of: Remove Unused Usings.  Pinch me!  Also, if you right-click the interface in a class’s definition (public class MyClass : Interface) there is an Implement interface option.   Last, if you are coding away and using a class before adding a using statement use ALT-Shift-F10 to automatically resolve the class and add the using statement to your file.
  • Improved support for debugging multithreaded applications
  • SQL Database Publishing Wizard is now integrated in the VS
  • Did I mention JavaScript debugging??!

 

You may notice I’ve omitted a few big topics.  I didn’t mention Ajax because that’s old news now.  However, there are new versions of the Ajax Control Toolkit and web deployment projects for VS2008.

 

I also didn’t mention Silverlight although I may find some interesting applications for it in the future.  For example, if you really hate writing JavaScript you could use Silverlight’s built-in mini CLR to write C# code which executes in the browser.  Oh, I hear it does some UI stuff too.

 

References: ScottGu 19-11-2007, ScottGu 13-03-2007, ScottGu 08-03-2007, C# 3.0 In a Nutshell, Pro ASP.NET 3.5 in C# 2008, and CodeProject.