Thom Robbins: Windows Forms Tips

Dataset,DataRow and other things

Sun, 08 Aug 2004 03:00:34 GMT

Question: I am trying to understand the dataset and how I can use it. It looks like a really powerful feature but it has an incredible amount of objects. It seems to me that I should be able to do simple things like create and edit values. But for the life of me I can’t seem to figure out how it works. Do you have some simple example that show how you can create a dataset and then update the individual rows?

Answer: Sure – here are some examples.

The following creates a dataset that we can use in the later examples.

' create the item table

Dim tblitem As DataTable = New DataTable("item")

Dim itemid As DataColumn = New DataColumn("itemno", _ Type.GetType("System.Int32"))

Dim colititle As DataColumn = New DataColumn("title", _ Type.GetType("System.String"))

Dim colipubdate As DataColumn = New DataColumn("pubdate", _ Type.GetType("System.String"))

Dim colidesc As DataColumn = New DataColumn("description", _ Type.GetType("System.String"))

Dim colilink As DataColumn = New DataColumn("link", _ Type.GetType("System.String"))

‘ create the columns

tblitem.Columns.Add(itemid)

tblitem.Columns.Add(colititle)

tblitem.Columns.Add(colipubdate)

tblitem.Columns.Add(colidesc)

tblitem.Columns.Add(colilink)

‘ add it to the dataset

ds.Tables.Add(tblitem)

Create a datatable from the dataset and insert a datarow.

Dim dt As DataTable = ds.Tables("item")

' get the datarow

Dim dtrow As DataRow

dtrow = dt.NewRow()

dtrow("itemno") = 10

dtrow("link") = "http://www.msn.com"

dt.Rows.Add(dtrow)

Select the new row and edit the value

Dim dr As DataRow() = dt.Select("itemno=10")

If dr.Length > 0 Then

dr(0).Item("link") = "http://www.test.com"

End If

dt.AcceptChanges()

Code Camp II: The Return!

Thu, 22 Jul 2004 15:20:34 GMT

*********CALL FOR SPEAKERS*********

Developer Code Camp II: The Return!

October 16/17, 2004

October 16 – 8:30 AM – 9PM

October 17 – 8:30 AM – 4PM

Microsoft Waltham

Schedule: http://radio.weblogs.com/0131777/CodeCamp2/code2.htm

General Call for Speakers

Code Camp II is looking for speakers and session leaders.

Code Camp II: The Return is looking to be even bigger and better than anything we have done before. The secret is you! This is a New England developer community based event that requires both speakers and attendees. The continuing goal of the Code Camps series is to provide an intensive developer to developer learning experience that is fun and technically stimulating. The primary focus is on delivering programming information and sample code that can be used immediately. The event is free and all slides, manuals and demo code are provided free!

This two day camp is hosted in our Waltham facility. As a community based event this is a general call for speakers and session leaders to help make this event a success. Based on your feedback, Code Camp II will now feature two types of 1.5 hour sessions and three defined tracks

Do you have something to say?

Requested Session Types:

Code focused presentation – These are presentations that include both power points and code demos. Given the audience that is attending it is important that a large amount of the presentation is focused on code and coding related techniques. Sample topics include How To and Best Practice Sessions.

Chalk Talks – These are new to the Code Camp. These sessions are designed as a facilitated discussion around a specific topic. No pre-canned demos, or pre-prepared code samples allowed! They are presented as a free form facilitated discussion that leverages the expertise of the presenter and the combined knowledge of the group to explore a specific topic.

Additionally, based on feedback we are sponsoring the following three tracks. All presentations must fall into these tracks to be considered. One of the strongest pieces of feedback from the last Code Camp was to provide a better organized set of tracks:

Code Camp Tracks:

Smart Client – This track is designed for presentations or chalk talks on topics related to Smart Client related development topics. This includes Windows Forms applications, Microsoft Office or mobile devices.

Web Track – This track is designed for presentations or chalk talks about Web based development that includes ASP.NET and Web Services.

Data Track – This track is designed for presentation and chalk talks about data storage technologies that includes SQL Server and XML.

********Submit Your Sessions********

Please complete the following and return it to trobbins@microsoft.com by September 15.

Once your session abstract is received we will review and provide scheduling for the selected sessions by October 1. All slides and code samples for the presentation must be delivered by October 14. If we are unable to fill all the time slots for the two days, the code camp will be shortened. It is the community that makes this event a success!

Name:
Company:
Email:
Phone:
Session Type:	Chalk Talk/Presentation (Select one)
Track:	Web/Smart Client/Data (Select one)
Level	200/300/400
Session Name:
Session Description:

Playing With Beta 1

Mon, 12 Jul 2004 00:38:25 GMT

Finally, got a chance to build an image using Visual Studio 2005 Beta 1. While writing some code I ran across something that I hadn’t seen in any of the documentation that I have read so far. I would typically use the following line to add a parameter to the SQL Command object.

sqlCmd = New SqlCommand

With sqlCmd

.Connection = sqlConn

.CommandTimeout = 30

.CommandType = CommandType.StoredProcedure

.CommandText = "spInsertFeedback"

.Parameters.Add("@EvaluatorName", EvaluatorName)

End With

According to the Intellisense that popped up, the Parameters.Add functionality has been made obsolete and now becomes.

sqlCmd = New SqlCommand

With sqlCmd

.Connection = sqlConn

.CommandTimeout = 30

.CommandType = Data.CommandType.StoredProcedure

.CommandText = "sp_GetCompanyName"

.Parameters.AddWithValue("@CustomerID", CustomerID)

End With

A Quick Observation

Wed, 30 Jun 2004 03:10:14 GMT

Had a chance to talk with a customer today that was moving their current application to .NET. During the course of the conversation we talked through some of the features and types within the framework. One thing that they didn’t understand was that in VB 6 Date, is really a double type in disguise. Within the Framework DateTime is actually a value defined within the Framework. For examples, you can instantiate and initialize a DateTime class using the following example:

Dim TestDate As New DateTime(2004, 1, 31)

MsgBox(TestDate)

Which returns the date 1/31/2004

Quick Directory Search

Tue, 22 Jun 2004 03:10:16 GMT

I got to spend the other day with a local customer that was making the shift to .NET. They were in the process of doing some prototyping their current application. They actually had a small VB application that was responsible for searching a local file share and returning a list of files that matched the search and their sizes. I put together the following snippet that I thought was interesting.

Imports System.IO

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim File

Dim Files() As fileinfo

Dim DirInfo As New DirectoryInfo("c:\")

Files = DirInfo.GetFiles("*.txt")

' display names

For Each File In Files

MsgBox("Name: " & File.Name)

MsgBox("Size: " & File.length.ToString)

End Sub

**Note**

The GetFiles operator accepts either the “?” or “*” search wildcards.

ADO.NET Best Practices

Sat, 05 Jun 2004 20:31:47 GMT

I really love talking to the local New England User Groups. I always have a great time and always manage to learn a few things myself. I think the information sharing at these groups really make it a worthwhile time investment. As I promised here are the slides and code samples for my talk on ADO.NET Best Practices.

Defining Interfaces

Tue, 11 May 2004 15:40:56 GMT

Interfaces help to define the various properties, methods and events that classes are able to implement. For developers these fine a small group of closely related properties, methods, and events. Additional feature and functionality can be added at any by adding additional interfaces and implementations. Prior to .NET Visual Basic was able to consume interfaces but not able to create them directly. With Visual Basic.NET the INTERFACE statement was introduced. This statement allows the definition of a true interface as a distinct entity from classes and to implement them using the IMPLEMENTS keyword. The following is a simple example of creating a CustomerManagement interface.

Public Class Customer

Interface CustomerManagement

Function AddCustomer(ByVal CustomerName As String, ByVal CustomerAddress As String, ByVal CustomerContact As String)

Function DeleteCustomer(ByVal CustomerName As String)

Function UpdateCustomer(ByVal CustomerName As String, ByVal CustomerAddress As String, ByVal CustomerContact As String)

End Interface

End Class

This interface is implemented by using the IMPLEMENTS keyword as shown below.

Once implemented the defined interface contains all the functions defined within the interface. Like a class, interfaces define a set of properties, methods and events. However, unlike classes, interfaces provide no direct implementation. They are implemented by classes defined as a separate entity from classes. Metaphorically, an interface represents a contract. Within this contract a class that implements an interface agrees to implements every aspect of that interface exactly as it is defined.

It is important to remember that interface implementations are allowed to evolve. However, the interfaces themselves shouldn’t be changed once they are published. Changes to the interface may break existing code that has implemented the interface. Once again, like a contract both parties in the contract agree never to change that implemented interface.

Reflection and Optional Parameters

Wed, 05 May 2004 22:48:42 GMT

I received an email about my previous post about optional parameters. The email asked about how you could do this through reflection. Actually pretty easy using the GetType and InvokeMember and you should be all set. The Type.Missing does the trick for passing the optional value. One thing to keep in mind is that if there is no default parameter specified within the function this will cause an exception.

Here is a short example:

Code in the form

Imports System

Imports System.Reflection

Public Class Form1

Inherits System.Windows.Forms.Form

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim o As New InvokeMe

Dim t As Type

t = GetType(InvokeMe)

' Will throw an error because there is no default value

't.InvokeMember("PassOptParam", BindingFlags.Public Or BindingFlags.Instance Or BindingFlags.InvokeMethod Or BindingFlags.OptionalParamBinding, Nothing, o, New Object() {Type.Missing, Type.Missing})

t.InvokeMember("PassOptParam", BindingFlags.Public Or BindingFlags.Instance Or BindingFlags.InvokeMethod Or BindingFlags.OptionalParamBinding, Nothing, o, New Object() {10, Type.Missing})

End Sub

Code in the class

Public Class InvokeMe

Public Function PassOptParam(ByVal Number1 As Integer, Optional ByVal Number2 As Integer = 5) As Integer

MsgBox(Number2) ' returns 5

End Function

End Class

The Optional Keyword

Wed, 05 May 2004 21:20:27 GMT

I received an email from somebody today asking about the optional keyword. By definition, keyword is used to indicate that a procedure or argument can be omitted when a procedure is called. Here is a simple example of how you could use it.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

PassOptParam(1)

End Sub

Private Function PassOptParam(ByVal Number1 As Integer, Optional ByVal Number2 As Integer = 5) As Integer

MsgBox(Number2) ' returns 5

End Function

Using XSLT - An Example

Sun, 02 May 2004 23:32:16 GMT

Using XSLT – An Example

I really like how I can use an XML document to separate the storage of application data from its presentation. The XML document contains a self describing set of data structures that I can define using my own vocabulary definitions. One of the major advantages of these documents is how easy they can be moved across the various process boundaries that exist within enterprises. This isolation of data into an XML allows a host processing the document to make the presentation decisions. An XML document by its very definition contains no formatting or presentation requirements. This is where the Extensible Stylesheet Language Transformation (XSLT) plays a major role. In this article I will show an example of how you can use XSLT to transform an XML InfoPath document in a Word 2003 document. More..

Creating and Moving Controls Dynamically within .NET

Sat, 24 Apr 2004 23:08:50 GMT

Question: I understand that .NET offers inheritance and I think that that may help with a project that I am currently working on. Let’s say that I have a single control. I want to use that control across multiple tabs on a form. How would I go about that?

Want to see my answer: Click Here

Smart Client Deployment

Thu, 25 Mar 2004 00:41:39 GMT

You can download the slides from my Live Meeting today on

Smart Client Deployment

This session will cover the issues and capabilities of Smart Client applications. The Smart Client is an application that runs outside of the browser taking advantage of the Windows Operating System. The biggest challenge to these applications has been their deployment and maintenance across thousands of clients. The .NET Smart Client directly addresses these issues while still taking advantage of the Internet protocols that power the distributed environments of today.

Slides are available here

What assemblies are running?

Wed, 24 Mar 2004 02:53:59 GMT

Reflection is the process of interrogating an assembly at run time to discover information about the various types that an assembly contains. There are actually all sorts of information that can be retrieved using Reflection. I was doing some coding with a customer and needed to check what assemblies were currently loaded into the application. The System namespace provides the AppDomain class that can be used to return a reference to the current application domain. The calling the GetAssemblies method this can be used to return a list of currently executing assemblies.

First, make sure that you import the Reflection class.

Imports System.Reflection

Then the following code is used to list the current loaded assemblies

Dim lasm As [Assembly]

For Each lasm In AppDomain.CurrentDomain.GetAssemblies

MsgBox(lasm.GetName.ToString)

Migrate Your Skills and Code to Visual Basic .NET

Tue, 09 Mar 2004 03:22:15 GMT

I have uploaded my slides for the presentation tomorrow.

Migrate Your Skills and Code to Visual Basic .NET

See how easy it is—and how much more productive you can be—building desktop applications in Visual Basic .NET. Key changes to the language, the runtime, data access, and deployment will help you understand how to bring your Visual Basic 6 development skills to Windows Forms desktop development in Visual Basic .NET. Also learn how to migrate your Visual Basic 6 code and applications and get up and running quickly.

You can download the slides from here

An Age Old Argument

Sun, 07 Mar 2004 03:44:51 GMT

While talking to some of the attendees at Dev Days last week, I happened to run across between two developers huddled into a corner of the lunch room. I was delighted to join their conversation around performance tips for writing applications. I was shocked to hear, they had concluded that SQL Server Stored procedures provided no performance advantages over dynamic SQL within applications.

Guys – SQL Server stored procedures improve performance on both Windows and ASP.NET applications. SQL Server automatically looks to optimize performance when a statement is saved as a stored procedure. SQL Server optimizes the commands and stores it in a compiled state, automatically making queries run faster than submitting them as an AD Hoc SQL statement. Also, when using stored procedures, the SQL Server managed provider is able to communicate natively. This automatically, shrinks the round trip time required to query and return the data.

I can safely say that it is ALWAYS good practice to forbid anything other than stored procedures when writing database code.

Edge 2004 Wrapup

Mon, 01 Mar 2004 12:51:21 GMT

I wanted to thank all that attended the Edge Conference 2004! The conference was without a doubt the best that I have seen. I wanted to thank all that attended the one day Smart Client Session. As requested, I have made this code available for download.

Distributed Programming using .NET Remoting

Wed, 04 Feb 2004 02:32:46 GMT

As promised here are the slides from today's webcast

Distributed Programming using .NET Remoting

This session will introduce the concepts and capabilities of .Net remoting and web services (a type of remoting). With .NET Remoting, Microsoft has vastly improved and simplified the process of building fast and scalable distributed systems. Microsoft started over and completely re-defined how applications communicate remotely. We will learn how to configure .NET remoting, when to use it, and what to watch out for when designing objects for remote use.

You can download the slides - Download Here

Retrieving Environmental Variables

Fri, 02 Jan 2004 02:22:54 GMT

Here is a quick way to retrive an environmental variable.

Dim CompName As String
CompName = Environment.GetEnvironmentVariable("COMPUTERNAME")

If you want to get a bit fancier, here is some sample code on retrieving all the environmental variables and placing them in a listview.

Dim compVariables As IDictionary
compVariables = Environment.GetEnvironmentVariables()

Dim CompVariable As System.Collections.DictionaryEntry

For Each CompVariable In compVariables
       Dim listitem As New ListViewItem(CompVariable.Key.ToString())
       listitem.SubItems.Add(CompVariable.Value.ToString())
       ListView1.Items.Add(listitem)
Next

Clearing Controls in a single loop

Tue, 30 Dec 2003 13:01:15 GMT

Here is an interesting code snippet. If you ever need to clear a large amount of text boxes on a form then the following code will do it. Of course based on the control type you can certainly change the type of control and you are off and running!

Dim ctrl As Control
For Each ctrl In Me.Controls
   If TypeOf ctrl Is TextBox Then
           ctrl.Text = ""
   End If
Next

Ensuring Single Application Instance

Sun, 21 Dec 2003 00:44:17 GMT

I was recently working with a local software development house that was completing a new release of their application. During a meeting with their development manager they had a rather unique question. They wanted to ensure that only a single copy of their application was running at any time. They hadn’t been able to figure out a simple way to accomplish this. In working with them we created the following code snippet that we embedded in the application startup.

Dim proc() As Process

'Determine the name of the current process

Dim modulename As String = Process.GetCurrentProcess.MainModule.ModuleName

Dim procname As String = System.IO.Path.GetFileNameWithoutExtension(modulename)

' retrieve any processes with this name

proc = Process.GetProcessesByName(procname)

If proc.Length > 1 Then

' there is more than one process of this name - END

MsgBox("Application currently running - only one instance allowed")

End

End If

Subclassing a Texbox

Wed, 03 Dec 2003 00:43:32 GMT

The paradigm of subclassing gives you a several advantages when developing code. Of course the most important is the ability to cleanly separate code into a front end and back end. Among other advantages this makes it easier for continued maintenance. Additionally, subclassing allows developers to cleanly encapsulate data within code that provides a more reusable code base. For this example, let’s create a sample project that subclass’ a textbox control in a Windows application that prevents a user from cutting values from a textbox. (CTRL-X)

Within a Windows application add a new class to the project called – scTextbox.vb
Within the class enter the following code:

Public Class scTextBox

Inherits TextBox

Private Const WM_CHAR As Integer = &H102

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)

' See if the CTRL key is being pressed.

If MyClass.ModifierKeys And Keys.Control Then

Select Case m.Msg

Case WM_CHAR

' Disable CTRL+X.

Select Case m.WParam.ToInt32

Case 24 'X = 24th letter of alphabet

' Do nothing here to disable the default message handling.

Case Else

'It is important to pass unhandled messages back to the default

‘ message handler.

MyBase.WndProc(m)

End Select

Case Else

'It is important to pass unhandled messages back to the default message

‘ handler.

MyBase.WndProc(m)

End Select

Else

'It is important to pass unhandled messages back to the default message handler.

MyBase.WndProc(m)

End If

End Sub

End Class

Close and save the Class
Drag a textbox control onto the form

Open the Windows Form within the project and within the code window expand the region marked “Windows Form Generated code”
Within this section of code replace all object creation instances that refer to the TextBox1 class with scTextbox as shown here.

#Region " Windows Form Designer generated code "

Public Sub New()

MyBase.New()

'This call is required by the Windows Form Designer.

InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.

Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)

If disposing Then

If Not (components Is Nothing) Then

components.Dispose()

End If

MyBase.Dispose(disposing)

End Sub

'Required by the Windows Form Designer

Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form Designer

'It can be modified using the Windows Form Designer.

'Do not modify it using the code editor.

Friend WithEvents TextBox1 As scTextBox

<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()

Me.TextBox1 = New SubClassExample.scTextBox

Me.SuspendLayout()

'TextBox1

Me.TextBox1.BackColor = System.Drawing.Color.Red

Me.TextBox1.Location = New System.Drawing.Point(24, 32)

Me.TextBox1.Name = "TextBox1"

Me.TextBox1.TabIndex = 0

Me.TextBox1.Text = "TextBox1"

'Form1

Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)

Me.ClientSize = New System.Drawing.Size(176, 78)

Me.Controls.Add(Me.TextBox1)

Me.Name = "Form1"

Me.Text = "Form1"

Me.ResumeLayout(False)

End Sub

#End Region

There are many other things that you can do with this basic concept. To download the sample project that I created CLICK HERE.

Retrieving RSS Data to a Windows Form

Sat, 29 Nov 2003 22:18:03 GMT

I am working on some interesting stuff with pulling and reading RSS data. One thing I wanted to get up fairly quickly is a little sample that can be used to retrieve and show RSS based data from a Windows Form DataGrid using five lines of code.

Dim reader As XmlTextReader = New XmlTextReader _("http://radio.weblogs.com/0131777/categories/datagridProgramming/rss.xml")

Dim ds As DataSet = New DataSet

ds.ReadXml(reader)

DataGrid1.DataSource = ds

Now that is cool!