Chris Garty's Weblog : Visual Studio 2005

Fun with Generics: BindingList and ReadOnlyCollection

chrisgarty — Thu, 16 Sep 2004 02:07:00 GMT

Mitch Denny's post about List events and Bill McCarthy's subsequent answer pointing him to BindingList had me looking at some Generics Design Guidelines and there were two generic collection types that I really glad I found out about.

Mitch's question ("why doesn't List<T> fire events") was similar to the one I was asking myself the other day. I was getting tired of providing Add and Remove methods on every object that managed a collection. For example, if I have an Order object and an OrderItem object, I can create Order.AddOrderItem, Order.RemoveOrderItem, but I'd really rather just expose a list of OrderItems from Order, validate each OrderItem as it is added, and allow the standard IList.Remove method to handle removals. It might not be something you'd want to do all the time, but it would mean less code and it could be a useful option to utilise in certain situations. BindingList<T> provides this useful 'list with events' capability.

The other generic collection type I was interested by was ReadOnlyCollection<T>. Have you ever used an IList (probably an ArrayList) internally to manage a list and provided a view of that by converting it to an array? Or maybe you've exposed an array externally? ReadOnlyCollection means that you have an option other than an array with the added benefit of being truly read-only i.e. it doesn't allow something like list[1] = 5;

Here are some tests I used to learn about BindingList<T>and ReadOnlyCollection<T> behaviour.

BindingListTests.cs…

using System;

using System.Collections;

using System.ComponentModel.Collections.Generic;

using NUnit.Framework;

namespace GenericsExamples

{

[TestFixture]

public class BindingListTests

{

bool _EventFired;

[Test]

public void TestBindingListEvents()

{

//Add to a bound list and fail if events are not triggered or triggered incorrectly.

BindingList<int> bindingList = new BindingList<int>();

bindingList.Add(1);

bindingList.ListChanged += new System.ComponentModel.ListChangedEventHandler(bindingList_ListChangedItemAdded);

_EventFired = false;

bindingList.Add(2);

if (!_EventFired) Assert.Fail("BindingList event not triggered");

bindingList.ListChanged -= new System.ComponentModel.ListChangedEventHandler(bindingList_ListChangedItemAdded);

bindingList.ListChanged += new System.ComponentModel.ListChangedEventHandler(bindingList_ListChangedItemDeleted);

_EventFired = false;

bindingList.Remove(2);

if (!_EventFired) Assert.Fail("BindingList event not triggered");

bindingList.ListChanged -= new System.ComponentModel.ListChangedEventHandler(bindingList_ListChangedItemDeleted);

Assert.AreEqual(1, bindingList.Count);

bindingList.ListChanged += new System.ComponentModel.ListChangedEventHandler(bindingList_ListChangedItemAddedButRejected);

bindingList.Add(5);

bindingList.ListChanged -= new System.ComponentModel.ListChangedEventHandler(bindingList_ListChangedItemAddedButRejected);

Assert.AreEqual(1, bindingList.Count);

}

void bindingList_ListChangedItemAdded(object sender, System.ComponentModel.ListChangedEventArgs e)

{

if (e.ListChangedType != System.ComponentModel.ListChangedType.ItemAdded)

{

Assert.Fail("Expected ItemAdded event but got: " + e.ListChangedType.ToString());

}

_EventFired = true;

}

void bindingList_ListChangedItemDeleted(object sender, System.ComponentModel.ListChangedEventArgs e)

{

if (e.ListChangedType != System.ComponentModel.ListChangedType.ItemDeleted)

{

Assert.Fail("Expected ItemDeleted event but got: " + e.ListChangedType.ToString());

}

_EventFired = true;

}

void bindingList_ListChangedItemAddedButRejected(object sender, System.ComponentModel.ListChangedEventArgs e)

{

if (e.ListChangedType == System.ComponentModel.ListChangedType.ItemAdded)

{

//Do some validation and if it fails then I might need to remove the added item

((IList)sender).RemoveAt(e.NewIndex);

}

ReadOnlyCollectionTests.cs…

using System;

using System.Collections.Generic;

using NUnit.Framework;

namespace GenericsExamples

{

[TestFixture]

public class ReadOnlyCollectionTests

{

[Test]

public void TestReadOnlyCollectionCreation()

{

List<int> list = new List<int>();

list.Add(1);

list.Add(2);

System.Collections.Generic.ReadOnlyCollection<int> roList = new ReadOnlyCollection<int>(list);

//roList.Add(3); //Operation isn't available!

//roList[1] = 3; //Operation isn't available!

Assert.AreEqual(2, list.Count);

Assert.AreEqual(2, roList.Count);

}

I wonder if they'll improve BindingList<T> before RTM by getting ListChangedEventHandler to pull the generic type from the BindingList rather than simply providing a parameter of "object sender"? We'll just have to wait and see.

For more about handling different situations with Generics, have a read of the Generics Design Guidelines from Krzysztof Cwalina.

Visual Studio 2005 Beta 1 Available

chrisgarty — Mon, 05 Jul 2004 19:59:00 GMT

After being announced last week, beta 1 of Visual Studio 2005 has just become available on MSDN Subscriber Downloads.

If you have an MSDN Universal license, go get it now!

Presentation: Refactoring

chrisgarty — Wed, 30 Jun 2004 22:00:00 GMT

Last week I gave a presentation at the Melbourne Microsoft Developer Group (MDNUG) on Refactoring with code examples in C# (.Net) and using Visual Studio 2005 for some live demonstrations.

The slide deck for my Refactoring presentation is available here.

Presentation: Agile .Net Development - Part 1 - Tools and Basics

chrisgarty — Wed, 30 Jun 2004 21:18:00 GMT

Last night I gave a presentation at the Melbourne Agile Developer Group (MXPEG) about agile .Net development. The group has a higher proportion of Java developers, so I had volunteered to give a view of agile from a .Net perspective.

I only got through half of my material last night, so I'll be talking again next month. Last night I presented information about a set of tools that can help if you are trying to follow some of the Extreme Programming practices while using .Net. Next month I'll be focusing on design decisions in .Net that have helped me create applications with a simple and testable design.

The practices covered were: Coding Standards, Continuous Integration, Refactoring, and Testing.

The technologies covered included: NUnit, NUnitAsp, NUnitAddin, NMock, PicoContainer, FxCop, CruiseControl.Net, NAnt, NCover, and Microsoft's yet-to-be-released Visual Studio Team System.

The presentation is available here.

OJB.Net and Generics

chrisgarty — Tue, 08 Jun 2004 21:57:00 GMT

I posted a little while ago about trying to use reflection with generic types. I have been trying to use a generic list type within OJB.Net (an object relational mapper for .Net).

I finished investigating this and thought I'd post a write-up about it here in case anyone else is using or wants to use OJB.Net and Generics together: http://weblogs.asp.net/chrisgarty/articles/150558.aspx.

VSTS: Getting coded web tests to run

chrisgarty — Fri, 04 Jun 2004 19:23:00 GMT

The coded web tests supported by the VSTS test tools really excite me. There are so many web test scenarios that I can now create very easily with a combination of recording and scripting. This will nicely complement the ASP.Net testing capabilities I already have thanks to NUnitAsp.

However when I recorded a web test, generated the code from the test, and then tried to use that test the test runner wasn't able to load my assembly. It gave me an error similar to this:

WebTestCoded Coded Web Test Error Could not run web test 'WebTestCoded' on agent 'MyComputer': Could not create instance of class 'WebTestCoded' :File or assembly name 'WebTestProject1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null', or one of its dependencies, was not found.

So I jumped on the Microsoft newsgroups and just got a reply to my query: You have to copy the assembly to VSDIR\Common7\IDE\PrivateAssemblies.

To help with this process, add a post build event similar to the one below to all projects with coded web tests: copy WebTestProject1.dll "C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\PrivateAssemblies"

Thanks to Eric Adams (PM - VSTS Test) for this solution!

Generics in OJB.Net (a.k.a. Generics Type Madness)

chrisgarty — Wed, 02 Jun 2004 22:50:00 GMT

At iP3 we are using OJB.Net for object relational persistence. It is really easy to use, but it was using an ArrayList by default and we wanted to use the new Whidbey Generics List<> type.

When OJB.Net creates objects out of the relational data, it uses reflection to generate the IList collection object which is ArrayList by default.

When we tried to change this to the Generics List<> type OJB.Net didn't seem to be able to handle it and reported that it couldn't find the type in the assembly. My collegue Lance and I sat and worked through the problem for about half an hour until he did a GetType().ToString() on a List<> object. To our surprise we found that the type name we needed to Reflect for was System.Collections.Generic.List'1 linstead of System.Collections.Generic.List.

The full line for getting the type for List<String> using reflection then becomes:

Type classType = Type.GetType(“System.Collections.Generic.List'1[[System.String,Mscorlib]],Mscorlib“,true);

Don Box has a good post about Generics reflection under the heading Generics as Type Constructors from August 2003, but it doesn't mention anything about adding a suffix to the type name.

If someone has seen this suffix notation explained previously then please shoot me a link.

Read more about the craziness on Lance's blog.

VS 2005 May CTP Installation Gremlins

chrisgarty — Sat, 29 May 2004 00:47:00 GMT

When installing the Visual Studio 2005 May Community Technology Preview, there are three key things to remember:

(1) Everything from the VS 2005 March CTP must be uninstalled before starting: MSDN, J#, .Net and VS.

(2) You cannot install the VS 2005 May CTP from DVD. I don't know why, but you have to copy it to a hard disk on your PC or somewhere on your LAN.

(3) After the May CTP .Net Framework has installed it will ask you to restart. Once the machine has restarted, the setup will run automatically but it will fail. You need to manually restart the setup process after this and it will continue on perfectly.

I don't know what the difference is between a hard disk and a DVD install. Maybe it is because of an error in my download of the ISO image. I wrote two DVD's and both exhibit this strange behaviour. If you have experienced this same behaviour, I'd love to hear from you so I can know whether or not this is a recurring problem.

Visual Studio Community Technology Preview May 2004 - Installed!

chrisgarty — Fri, 28 May 2004 08:58:00 GMT

I had some initial trouble installing the May Community Technology Preview (CTP), but after reading the instructions (what a novel idea!) I realised that I just needed to remove all the March components: MSDN, J#, framework, and Visual Studio (VS). Keep an eye on this when you install it, since it doesn't give you much information in the error messages.

I helped give a talk at the Melbourne .Net User Group last night about the new VS Team System (nee: Burton), and so I was really looking forward to using the tools that I had learned so much about. I'm pleased to report that it really is as simple to use and powerful as the website and the videos suggest.

The web testing tool in VSTS is excellent. It is very simple to use and should support a wide variety of web applications. I tried it on a web application containing ASP.Net, plain HTML, Macromedia Flash, and Javascript and it worked beautifully first time. Web tests can be created either by demonstration (recording), or by hand coding in C# and VB.Net. The recording feature enables any VS user to create automated regression tests very quickly. I know a couple of people that will be very interested in the ability to automate their manual regression testing.

Over the next week I'll post some more information about the changes I notice from the March CTP and some more information about the VSTS client tools.

Visual Studio Team System in May CTP

chrisgarty — Thu, 27 May 2004 18:18:00 GMT

My download of the May CTP is complete. The installation process includes an informative message about VSTS:

Welcome to the Visual Studio 2005 Community Technology Preview May 2005 DVD

This Community Technology Preview includes functionality from the Visual Studio Team System, a new suite of software lifecycle tools that will ship with Visual Studio 2005. In the summer of 2005, we will release a Beta of Visual Studio. Please be aware that this Beta will not include the Team System functionality. We hope to release a formal Beta of the Team System by the end of the year. We're providing this early look at the Team System functionality so that we can get feedback on the product and make any necessary changes to our plans.

All previous caveats about the Community Technology Preview program apply to this build: don't install it on machines you care about, be aware that you may have to reformat your drive in order to completely uninstall, and the feature set is incomplete and unstable in many ways. The purpose of these builds is to help you contribute to the development process.

To that end, please submit any and all comments, feedback, or concerns to: http://msdn.microsoft.com/whidbey/newsgroups.

We look forward to hearing from you.

Thank you!

I'll do a post later about the VSTS functionality available. Installing now... :)

ObjectSpaces delay discussions

chrisgarty — Wed, 26 May 2004 22:21:00 GMT

Some people are taking the ObjectSpaces delay a little harder than others.

I first met Robert McLaws when he hosted the PDC 2003 Object Relational BoF session. I just read one of his recent posts where he argues that the ObjectSpaces delay is good since it is good to get things right the first time. He also tells the people who are disappointed to that their “mentality” is “ridiculous” and that they should “Grow up. Seriously.”.

I think this is a little harsh on the people who were starting projects to hit the market in 2005 that would have used ObjectSpaces. I don't think it is a bad thing for Microsoft to hear that their schedule changes affect ISV's and other customers.

I personally am grateful that Microsoft has delayed ObjectSpaces to combine it with the WinFS work. Making application data as accessible as files in the OS is a brilliant move.

Hopefully when Longhorn comes out we'll be a lot closer to the holy grail of “no more data silos”.

Latest Visual Studio Community Tech Preview (May) is available

chrisgarty — Wed, 26 May 2004 21:24:00 GMT

The latest Visual Studio (VS) Community Tech Preview (CTP) is available via MSDN subscriber downloads.

The most interesting part for those that are already familiar with the March VS CTP will be inclusion of Visual Studio Team System (VSTS). You can find out the full details about VSTS via my earlier blog entry and the official VSTS site.

Tim Sneath reports from TechEd that the May VS CTP will include the (VSTS) client tools, but not the server tools. I would have found out myself, but the download still has 7 hours to go ;).

Visual Studio Team System Announced

chrisgarty — Tue, 25 May 2004 23:21:00 GMT

There are interviews on TheServerSide and a good collection of links on Chris Sells' blog.

The unit testing and code coverage tools look fantastic in the videos. The ability to increase the amount of communication through a simple integrated tool is going to be a great bonus for teams of any size.

I wonder how this will play with NUnit? Will we integrate existing NUnit tests into the VSTS suite or migrate the tests over to VSTS? Investigation time...

ObjectSpaces and MBF both delayed till Longhorn

chrisgarty — Mon, 24 May 2004 21:50:00 GMT

First we learned that MBF has been delayed till Longhorn (from Tim Brookins) and now ObjectSpaces is adopting the same schedule. The official announcement is here.

I wonder if ObjectSpaces was delayed and that caused the MBF re-schedule, since MBF uses ObjectSpaces for persistence. Either way, because of the extra time, they'll both be stronger and more tightly integrated when they do get released.

Ouch: MBF delayed till Longhorn wave

chrisgarty — Tue, 11 May 2004 22:56:00 GMT

Tim Brookins, an architect on the MBF team, has reported that MBF is no longer in the Whidbey wave and instead will be in the Longhorn wave.

This is an exciting area of technology for Microsoft since it touches so many 'hot' areas: Microsoft's business application development (Green), service oriented architecture (Indigo), object relational persistence (ObjectSpaces), lightweight process support (in-process Biztalk process engine), and model driven architecture (Whitehorse) to name a few.

It is a shame that business application developers won't be able to start using the base classes to build business logic, but Tim points out that “collapsing MBF into a single release [will] be more beneficial for our customers” will allow MBF to focus solely on Longhorn. This is an exciting effort and one that I'll be watching carefully over the next 2 years.