.NET

Developer: Utilizing .NET Generics to write better code by Shawn Weisfeld @ UT Dallas .NET UG on 02/27/2010

Shawn Weisfeld — Thu, 25 Feb 2010 01:45:54 GMT

This Saturday (2/27) I will be giving my .NET Generics talk for the UT Dallas .NET UG in Richardson TX. If you are in the area please check it out (http://www.usergroupsupportservices.com/UGEventView.ugss?EventID=9160). If you cannot make it but are interested in seeing the talk, you can watch it online.

Abstract:
Generics let you tailor a method, class, structure, or interface to the precise data type it acts upon. In this session we will discuss what capabilities Generics provide to you the developer and how to use them in collections, and with delegates. We will also talk about creating your own generic classes and methods.

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PowerPoint & Demos

Bio:
Shawn Weisfeld (shawn@shawnweisfeld.com) is a Staff Developer at a fortune 100 company, currently located at Dallas TX facility. There he specializes in intranet & smart client development for internal line of business applications. Besides his day job Shawn also is an Adjunct Professor at The Florida Institute of Technology (http://www.fit.edu). He also does freelance software development work for local small businesses and training. In his free time he volunteers with INETA NorAm (http://www.ineta.org) and is a member of the Board of Directors and Mentor for North Texas. Shawn started his career at his family business in Port St. Lucie FL while working on his undergraduate degree in Business Administration at the University of Central Florida and after a year off Shawn moved back to Orlando to pursue a Masters degree in Management Information Systems at The University of Central Florida and has since earned a second Masters degree in Computer Information Systems from Florida Institute of Technology. Shawn was awarded the Microsoft C# Most Valuable Professional award for 2007 - 2010. Shawn is an avid technology presenter and since July of 2005 Shawn has presented at many user group events, and even got to speak at the launch of Visual Studio. Shawn has served as the President of the Orlando .NET UG (http://www.onetug.org) from 2006 – 2008, and started the Developer Round Table UG (http://www.developerroundtable.com) in 2009. Shawn regularly attends, and records for INETA LIVE (http://live.ineta.org), many of the local user groups in the D/FW metroplex, including; D/FW Connected Systems UG, Dallas .NET UG, Dallas ASP.NET UG, Dallas C# Programming Sig, Dallas VSTS UG, North Dallas .NET UG, North Texas PC UG, UT Dallas .NET UG. So be sure to say hello if you see him.

Property Causing a Stack Dump

sweisfeld — Tue, 16 Jun 2009 05:26:50 GMT

Got a call today, someone was getting a stack dump every time they tried to assign a value to a property. Here is a screen print of the problem they were having. can you spot the problem?

If you said that the property is calling itself you get a gold star. What was happening is that every time we tried to set the Name property, it calls the Name property to set it, and that called the Name property, and that called the Name property, over and over again, till .NET stack dumped. We are missing a backing variable.

By backing the property with a private variable, it removes the infinite recursion. Since the variable itself is private nobody can see it, or can use it outside the class, they are forced to use the property, and all is right with the world again!

Populating a Generic List in VB.NET

sweisfeld — Tue, 16 Jun 2009 05:17:35 GMT

Got a question on how to populate a generic list in VB.NET, and while I am a C# guy, I figured I would show some VB.NET love.

For this example I will be using a customer class, he is real simple just 2 properties. One for first name and one for last name.

   1:  Public Class Customer

2:

   3:      Private _first_name As String

   4:      Public Property FirstName() As String

   5:          Get

   6:              Return _first_name

   7:          End Get

   8:          Set(ByVal value As String)

   9:              _first_name = value

  10:          End Set

  11:      End Property

12:

  13:      Private _last_name As String

  14:      Public Property LastName() As String

  15:          Get

  16:              Return _last_name

  17:          End Get

  18:          Set(ByVal value As String)

  19:              _last_name = value

  20:          End Set

  21:      End Property

22:

  23:  End Class

Now that I have a class I can new up a list of that type:

   1:  Dim customers As New List(Of Customer)

Now I can create an object of type customer set its properties and add it to the list:

   1:          Dim c As New Customer

   2:          c.FirstName = "Shawn"

   3:          c.LastName = "Weisfeld"

   4:          customers.Add(c)

That is a bit tedious, lets simplify using the with statement:

   1:          Dim c2 As New Customer

   2:          With c2

   3:              .FirstName = "Shawn"

   4:              .LastName = "Weisfeld"

   5:          End With

   6:          customers.Add(c2)

Still too long, how about we create a constructor by adding the following code to our customer object: (NOTE: that I create 2 constructors, the first one that has no parameters is created by us automatically by VB.NET, however when we specify our own constructor VB.NET doesn’t give us the default one for free, so we have to code him up, assuming we wanted to have a parameter-less constructor)

   1:      Public Sub New()

2:

   3:      End Sub

4:

   5:      Public Sub New(ByVal first_name As String, ByVal last_name As String)

   6:          Me.FirstName = first_name

   7:          Me.LastName = last_name

   8:      End Sub

Now that I have the constructor I can now new up the customer and add him to my list in one line of code:

   1:          customers.Add(New Customer("Shawn", "Weisfeld"))

Well that is all good, but what if we don’t own the class and cannot add constructors. Well VS.NET 2008 (.NET 3.5) includes something called Object Initializers:

   1:          Dim c3 = New Customer() With {.FirstName = "Shawn", .LastName = "Weisfeld"}

   2:          customers.Add(c3)

That is better and we can even get it to a 1 line-er:

   1:          customers.Add(New Customer() With {.FirstName = "Shawn", .LastName = "Weisfeld"})

Now your objects can go forth an multiply!

Couldn't attend MIX 09?

sweisfeld — Tue, 19 May 2009 05:23:08 GMT

We are bringing MIX to the DFW area, but instead of repeating the MIX conference, we are boiling down the best of MIX into a 1-day hands on lab. This community event, called MIX Notes, will provide hands-on examples presented by industry leaders.

Computers will be provided, but participants are welcome to bring their own laptops.

Where:                                 Tekfocus (in the InfoMart)
When:                                  June 20, 9 AM - 4 PM
Registration Fee:   $25

* Lunch will be provided

Are you Coming to the Dallas Tech Fest 2009?

sweisfeld — Sun, 10 May 2009 03:15:09 GMT

I will be speaking at the Dallas Tech Fest, but that should not prevent you from coming. . .

System namespace conflict in SAP web services

sweisfeld — Fri, 17 Apr 2009 16:55:41 GMT

My colleague, Jerome Nicolas, found a solution the problem outlined below and since he doesn't have a blog and we thought this was some great information we decided to post it to mine. Hope it helps.

Scenario: adding a web reference in Visual Studio to an SAP web service that was created from a remotely enabled function module with a table parameter associated type BAPIRET2.

Problem: The ABAP object BAPIRET2 is typically used to return messages when calling a BAPI, but it contains a field named “SYSTEM” which can conflict with the System namespace in .NET. If you create a web service from a function module that uses BAPIRET2 and try to set up a web reference in Visual Studio, you’ll get a build error like this:

An object reference is required for the nonstatic field, method, or property 'SAPWebService.SAPWebRef.Bapiret2.System.get'

for every line in Reference.cs that looks like this:

System.Xml.Serialization.XmlElementAttribute(Form=System.Xml.Schema.XmlSchemaForm.Unqualified)]

Solution: To avoid this error without having to change the code in all your .NET applications that consume these web services, you can create a copy of BAPIRET2 in SAP and rename the SYSTEM field. In this case, we copied BAPIRET2 to ZRFC_BAPIRET2_TAB and renamed the SYSTEM field to SYSTEMSAP.

Original BAPIRET2:

New object ZRFC_BAPIRET2_TAB

Then in your function module, use the new object instead of BAPIRET2.

Now when you run the SAP web service wizard, it generates a WSDL with the new SYSTEMSAP field. And viola! No more build errors.

What do your error messages reveal?

sweisfeld — Mon, 09 Mar 2009 17:46:00 GMT

I know that most of you all know this already, but I figured it was worth a blog post since I just saw this from http://www.autosite.com. I got this very informative error message back when using their site earlier. . .

Query Of Queries runtime error.
Expected type STRING but encountered type NULL on the left of the LIKE condition
The error occurred in D:\INETPUB\wwwroot\content\Research\kbb\act_valueReport.cfm: line 74
Called from D:\INETPUB\WWWROOT\content\Research\kbb\index.cfm: line 21
72 :
73 : <cfmodule template="mod_kbbtable.cfm" width="#kbbModTableWidth#">
74 : <cfquery dbtype="query" name="qEquip">
75 : SELECT * FROM valueReport.Equipments WHERE GroupCode LIKE 'M' ORDER BY DisplayOrder
76 : </cfquery>

While it is important for us as developers to log this type of information, there is NO reason for us to show it to our customers. Now I know table names, physical paths, and other good stuff. In your asp.net applicaitons make sure you set your customer errors to “On” (http://msdn.microsoft.com/en-us/library/h0hfz6fc.aspx). You also want to make sure that you have logging so that you as the developer can triage errors.

Oh and here is a BONUS TIP: Don’t use Select *, in most cases you don’t need all the columns and there is no reason to have the DB send them all back. . . .

Let’s start a campaign to call out any website that we see on the internet that doesn’t properly hide their dirty laundry.

A review of Professional DotNetNuke 5: Open Source Web Application Framework for ASP.NET from Wrox

sweisfeld — Sun, 01 Mar 2009 07:12:00 GMT

A few weeks ago I got a copy of Professional DotNetNuke 5: Open Source Web Application Framework for ASP.NET (http://www.amazon.com/Professional-DotNetNuke-Application-Framework-ASP-NET/dp/0470438703/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1235867832&sr=8-1). Figured since I had been to presentations by 3 of the 5 authors I just had to have the book. Brian Scarbeau, Stan Schultes and Ryan Morgan are avid speakers in the Florida .NET community and knowing them I knew this book was going to be a good read. A cross country flight from Dallas Texas to Seattle Washington provided the perfect opportunity to concentrate on reading a new book.

While waiting for my plane to take off I made it through the first chapter of the book written by the father of DotNetNuke Shaun Walker. This chapter talks about the history of where DNN came from and trials and tribulations that Shaun and his team had giving birth to what we know today. I think that anyone that is interested in starting an open source product should spend a few minutes and learn from the lessons that Shaun learned in the creation of DNN, especially if you are trying to build an open source product that sits on the very not open source Windows platform.

The next few chapters of the book provide information on just about everything that administrator/end-user would need to know in order to go from an empty hosting account to having a DNN site. This includes installation, an overview of the modules and how to administer the lot. The next chunk of the book talks about the architecture of DNN. For years I have been telling developers looking for reference architectures to look at products like DNN. This set of chapters not only includes information on how the DNN team did what they did, but perhaps more importantly WHY they did it that way. For me knowing the why behind these types of decisions allows me to leverage the lessons learned by other developers and apply that to my applications, even non-DNN applications. The ability to learn from the experience/knowledge/mistakes of others makes us all better developers. The last chunk of the book is the how to information that you need to extend DNN. They cover modules, skinning, and distribution.

This book provides a good overview of all the major components in the DNN products. It covers the architecture of the DNN infrastructure and how to extend it with your own custom modules and skins. This book provides the developer and the administrator what they need to get their feet wet with DNN, and as an added bonus you get a great narrative on the birth of an open source software package.

BTW: At the time I wrote this DNN was the second most popular download on codeplex with just fewer than 20,000 downloads in the last 7 days. The only thing that beat it was a plug-in for World of Warcraft.

Oh and when my family needed a website for their small business guess what they got? (http://www.apickygourmet.com)

SharePoint WebServices are your friend

sweisfeld — Wed, 25 Feb 2009 00:50:00 GMT

Ever wanted access to that treasure trove of information available in SharePoint lists scattered across your enterprise? Ever wanted to provide a quick and dirty UI for users to enter data, but need to have programmatic access to the data? Use SharePoint! SharePoint provides WebServices that give you access to just about everything you can think of (http://msdn.microsoft.com/en-us/library/ms954015.aspx). For the purposes of this article I am going to use the Lists WebService to 1) get data from a list, 2) Add an item to the list and 3) Delete an item from the list.

The first step is to add two service references to Sharepoint. The first is to the Lists WebService (http://server/_vti_bin/Lists.asmx), and the second is to the Views WebService (http://server/_vti_bin/Views.asmx). Before you go and add the services references you need to ensure you have permissions to the service. You do this by putting the url to the asmx in the browser and adding "?WSDL" to the end. If you get a blank html page then you do NOT have permissions to that service, well at least for that node. In my environment I only have permissions to a sub site in SharePoint. To that end I had to point directly to the WebService for the SharePoint site that I have access to. For example the address that I have to use is (http://server/site1/subsite2/subsite3/subsite4/_vti_bin/Lists.asmx). So after you ensured you have the correct URL you can now add the service references to your project. Easy enough to do right click on the project in the solution explorer in VS.NET and select "Add Service Reference" (Note I am using VS.NET 2008).

Now that you have your 2 service references you need to check your WCF configuration in the app/web config file. Due to my environment I had to set it to the following:

1: <security mode="TransportCredentialOnly">

2:     <transport clientCredentialType="Ntlm" proxyCredentialType="None"

3:         realm="" />

4:     <message clientCredentialType="UserName" algorithmSuite="Default" />

5: </security>

The next step is to get the ID’s for the List and View that you want to pull the data for. The code below converts the name or title of the list/view into the ID. From what I read it is recommended that you use the ID’s however passing in the name to the web methods will work in most cases.

1:         private static string GetListID(string listName)

2:         {

3:             //Find the list we want

4:             string listID = null;

5:             ListsSoapClient ws = new ListsSoapClient();

6:             try

7:             {

8:                 XDocument doc = XDocument.Parse(ws.GetListCollection().OuterXml);

9:                 listID = (from x in doc.Elements().First().Elements()

10:                           where x.Attribute("Title").Value.Equals(listName)

11:                           select x.Attribute("ID").Value).FirstOrDefault();

12:             }

13:             catch (TimeoutException timeout)

14:             {

15:                 //Handle the timeout exception.

16:                 ws.Abort();

17:             }

18:             catch (CommunicationException commException)

19:             {

20:                 // Handle the communication exception.

21:                 ws.Abort();

22:             }

23:

24:             Console.WriteLine("\n\nI found that List '{0}' has ID '{1}'", listName, listID);

25:             return listID;

26:         }

1:         private static string GetViewID(string viewName, string listID)

2:         {

3:             //Find the view we want

4:             string viewID = null;

5:             ViewsSoapClient ws = new ViewsSoapClient();

6:             try

7:             {

8:                 XDocument doc = XDocument.Parse(ws.GetViewCollection(listID).OuterXml);

9:                 viewID = (from x in doc.Elements().First().Elements()

10:                           where x.Attribute("DisplayName").Value.Equals(viewName)

11:                           select x.Attribute("Name").Value).FirstOrDefault();

12:

13:             }

14:             catch (TimeoutException timeout)

15:             {

16:                 // Handle the timeout exception.

17:                 ws.Abort();

18:             }

19:             catch (CommunicationException commException)

20:             {

21:                 //Handle the communication exception.

22:                 ws.Abort();

23:             }

24:

25:             Console.WriteLine("\n\nI found that View '{0}' has ID '{1}'", viewName, viewID);

26:             return viewID;

27:         }

With all the plumbing out of the way I can now call the service to retrieve all the data in my list.

   1:          private static XDocument GetListData(string listID, string viewID)

   2:          {

   3:              XDocument list_data = null;

   4:              ListsSoapClient ws = new ListsSoapClient();

   5:              try

   6:              {

   7:                  list_data = XDocument.Parse(ws.GetListItems(listID, viewID, null, null, null, null, null).OuterXml);

   8:                  var q = (from x in list_data.Elements().First().Elements().First().Elements()

   9:                           select new

  10:                           {

  11:                               Title = x.Attribute("ows_LinkTitle").Value,

  12:                               Field1 = x.Attribute("ows_Field1").Value,

  13:                               Field2 = x.Attribute("ows_Field2").Value

  14:                           });

15:

  16:                  Console.WriteLine("\n\nThe List has the following items");

  17:                  foreach (var r in q.ToList())

  18:                  {

  19:                      Console.WriteLine("{0}\t{1}\t{2}", r.Title, r.Field1, r.Field2);

  20:                  }

  21:              }

  22:              catch (TimeoutException timeout)

  23:              {

  24:                  // Handle the timeout exception.

  25:                  ws.Abort();

  26:              }

  27:              catch (CommunicationException commException)

  28:              {

  29:                  // Handle the communication exception.

  30:                  ws.Abort();

  31:              }

32:

  33:              return list_data;

  34:          }

I can also Add an item to the list:

   1:          private static void AddListItem(string listID)

   2:          {

   3:              //Add List Item

   4:              XElement new_item = new XElement("Batch",

   5:                  new XAttribute("OnError", "Continue"),

   6:                  new XAttribute("ListVersion", "1"),

   7:                  new XElement("Method",

   8:                      new XAttribute("ID", "1"),

   9:                      new XAttribute("Cmd", "New"),

  10:                      new XElement("Field",

  11:                          new XAttribute("Name", "Title"),

  12:                          "New Title"),

  13:                      new XElement("Field",

  14:                          new XAttribute("Name", "Field1"),

  15:                          "new field 1"),

  16:                      new XElement("Field",

  17:                          new XAttribute("Name", "Field2"),

  18:                          "new field 2")));

19:

  20:              ListsSoapClient ws = new ListsSoapClient();

  21:              try

  22:              {

  23:                  Console.WriteLine("\n\nAdding Item to the list . . .");

  24:                  Console.WriteLine(ws.UpdateListItems(listID, new_item.GetXmlElement()).OuterXml);

  25:              }

  26:              catch (TimeoutException timeout)

  27:              {

  28:                  // Handle the timeout exception.

  29:                  ws.Abort();

  30:              }

  31:              catch (CommunicationException commException)

  32:              {

  33:                  // Handle the communication exception.

  34:                  ws.Abort();

  35:              }

  36:          }

And delete an item from the list:

   1:          private static void DeleteListItem(string listID, string item_id)

   2:          {

   3:              ListsSoapClient ws = new ListsSoapClient();

   4:              try

   5:              {

   6:                  XElement delete_item = new XElement("Batch",

   7:                          new XAttribute("OnError", "Continue"),

   8:                          new XAttribute("ListVersion", "1"),

   9:                          new XElement("Method",

  10:                              new XAttribute("ID", "1"),

  11:                              new XAttribute("Cmd", "Delete"),

  12:                              new XElement("Field",

  13:                                  new XAttribute("Name", "ID"),

  14:                                  item_id)));

15:

  16:                  Console.WriteLine("\n\nDeleting Item to the list . . .");

  17:                  Console.WriteLine(ws.UpdateListItems(listID, delete_item.GetXmlElement()).OuterXml);

  18:              }

  19:              catch (TimeoutException timeout)

  20:              {

  21:                  // Handle the timeout exception.

  22:                  ws.Abort();

  23:              }

  24:              catch (CommunicationException commException)

  25:              {

  26:                  // Handle the communication exception.

  27:                  ws.Abort();

  28:              }

  29:          }

BTW the web service takes a XmlElement but I like working with the new XElement better. I altered an extension method Eric White wrote that does the conversion.

   1:          public static XmlElement GetXmlElement(this XElement element)

   2:          {

   3:              using (XmlReader xmlReader = element.CreateReader())

   4:              {

   5:                  XmlDocument xmlDoc = new XmlDocument();

   6:                  xmlDoc.Load(xmlReader);

   7:                  return xmlDoc.FirstChild as XmlElement;

   8:              }

   9:          }

There are a bunch of libraries out there to aid in this process. The one that has got me the most excited is LINQ to SharePoint http://www.codeplex.com/LINQtoSharePoint.

Ramp Up

sweisfeld — Tue, 06 Jan 2009 18:08:00 GMT

Microsoft has started a new program called Ramp UP (http://msdn.microsoft.com/en-us/rampup/default.aspx). “Ramp Up is a free, online, community-based learning program, with a number of different tracks that will help you build your portfolio of professional development skills. Ramp Up has a solid foundation of premium technical content from subject-matter gurus, and provides easy-to-access content in a variety of forms that guide you in learning the important skills.”
At this time they have 6 tracks. . .

SharePoint for Developers (Part 1)
Visual Studio 2008
Aspiring Developer (migrating to VS 2005)
Java Developer (migrating to VS 2005)
VB 6.0 Developer (migrating to VS 2005)
VS 2002/2003 Developer (migrating to VS 2005)

Check it out!