Incremental Intellisense Improvements in VS2010

by Paul Kimmel

Learn about the history of debugging and evolutionary improvements in Intellisense in VS2010.


Some improvements like LINQ are substantial, and some just make our lives a little easier. Intellisense in VS2010 has an improvement that is incremental and will make the life of a programmer a little easier.

In VS2008 Intellisense listed members alphabetically by matching characters as you type them. In VS2010 Intellisense lists members using a contains-a approach. Let's take a few minutes to explore this incremental improvement to the VS2010 IDE.

Evolution Lived

In a very early version of C++ I realized one could modify the basic IO functions like printf and add a second version of the methods that wrote directly to a second video buffer. The primary implementation of these methods wrote to the primary video and comprised the programs output. By adding a second monitor-a CGA monitor-and adding the equivalent of trace statement and sending them to the CGA video memory you can have your primary output, which in those days was a text-based GUI-display, on your primary monitor and trace statements appear on the CGA monitor. Viola! Two monitors in the days before it was en vogue.

Video buffer memory is still accessible. To see this open a cmd window, run the debug.exe program and send some data right to video memory. (For the demo I am using EGA video memory because I can't recall the CGA video memory addresses.) It is worth noting that odd numbered memory addresses at EGA memory represent the background and foreground RGB colors, and that my typographic errors (shown in Figure 1) show you just how error prone this approach can be (which in turn demonstrates why good debugging tools were and still are so necessary).

RGB Grid
Click here for larger image

raw data right into EGA video memory
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Figure 1: Entering the raw data right into EGA video memory will display ASCII characters and RGB colors directly to video memory.

Thankfully debugging evolved shortly thereafter with Borland's Turbo Pascal Integrated Development Environment (IDE) and continue to evolve today. Now we have built-in Output windows and Intellisense that make debugging what's going on and figuring out what code base we have to work with substantially easier. (To demonstrate Intellisense for VS2010 I will demonstrate how to redirect IO using .NET in the section "The New and Improved Intellisense".)

Intellisense in Visual Studio 2008

Intellisense in Visual Studio works by displaying members alphabetically. When you type an object name followed by the member of an operator (.) and some alpha-numeric characters Visual Studio will display a drop down window, the first member that start with those characters and then the members that follow alphabetically. Visual Studio 2010 improves on this approach.

The New and Improved Intellisense

When you type an object name, followed by the member of operator in Visual Studio 2010, Visual Studio will display all of the members that start with or contain those characters. Instead of a starts-with, alphabetic listing, Visual Studio 2010 displays a list of members that contain those characters anywhere in the member name, as long as those characters are in the same relative order and the case matches.

To demonstrate, the code in Listing 1 shows you how to redirect console IO to a WinForm of your choosing, instead of the IDE's Output window. I will use this code to show you how Intellisense lists members in VS2010. (Listing 2 shows you how to add a TextBox to a form and initialize the MyStreamWriter class with the TextBox, resulting in Console Write and WriteLine method calls buffering data in the Form's TextBox.)

Listing 1: Building your own debug window in VS2010 using console IO redirection.

  Imports System.Windows.Forms
  Imports System.Text
  Public Class MyStreamWriter
    Inherits System.IO.TextWriter
    Private control As TextBoxBase
    Private Builder As StringBuilder
    Public Sub New(ByVal control As TextBox)
      Me.control = control
      AddHandler control.HandleCreated, _
         New EventHandler(AddressOf OnHandleCreated)
    End Sub
    Public Overrides Sub Write(ByVal ch As Char)
    End Sub
    Public Overrides Sub Write(ByVal s As String)
      If (control.IsHandleCreated) Then
      End If
    End Sub
    Public Overrides Sub WriteLine(ByVal s As String)
      Write(s + Environment.NewLine)
    End Sub
    Private Sub BufferText(ByVal s As String)
      If (Builder Is Nothing) Then
        Builder = New StringBuilder()
      End If
    End Sub
    Private Sub AppendText(ByVal s As String)
      If (Builder Is Nothing = False) Then
        Builder = Nothing
      End If
    End Sub
    Private Sub OnHandleCreated(ByVal sender As Object, _
       ByVal e As EventArgs)
      If (Builder Is Nothing = False) Then
        Builder = Nothing
      End If
    End Sub
    Public Overrides ReadOnly Property Encoding() As System.Text.Encoding
        Return Encoding.Default
      End Get
    End Property
  End Class

Listing 2: Initialize MyStreamWriter with a TextBox residing on a form to send Console IO to the TextBox instead of a command window or the Output window in Visual Studio/

  Public Class Form2
    Private writer As MyStreamWriter = Nothing
    Private Sub Form1_Load(ByVal sender As System.Object, _
       ByVal e As System.EventArgs) Handles MyBase.Load
      writer = New MyStreamWriter(TextBox1)
    End Sub
  End Class

Look at the Inherits System.IO.TextWriter statement in Listing 1. If you type System.IO. then Intellisense in Visual Studio 2010 will start with an alphabetic listing of members. When you start typing the listing is refined. If you type capital T, as in System.IO.T, instead of an alphabetic listing with members starting with T Intellisense will list all members starting with or containing a capital T. In Visual Studio 2010 a capital T will result in PathTooLongException,TextReader, and TextWriter. The logic here being what's the point of listing members that have no T just because they precede or follow members with T alphabetically.

Continuing the above scenario if you type System.IO.TW then the TextWriter method will be displayed because TextWriter is the only member with a capital T and W in that order (even though there are letters in between).


Intellisense has been incrementally improved in Visual Studio 2010. Instead of a associative alphabetic listing only members that contain the actual letters you type are displayed. If a member doesn't contain one of your letters then the member is filtered out.

The historical perspective on dual monitor debugging and tracing was added because in part this is the kind of thing that floats in my head. However, it may be interesting to newer developers to learn something about the ongoing existence of older solutions and contrast those to how much things have improved. Programmers used to have to memorize everything before Intellisense, and debugging was a painstaking process of manually examining code and write line statements. Integrated debuggers and trace windows are a relatively new invention, spanning a period of less than one person's career in computer science.

The sample code was added just so you'd have some code to chew on to play with Intellisense. The console redirect technique is a nice tool to keep around and it is fun to play with, but you can use any code to explore the changes to Intellisense. (The console code was originally published as "Redirect I/O to a TextBoxWriter in .NET" in April, 2006.)

About the Author

Paul Kimmel is the VB Today columnist for CodeGuru and has written several books on object-oriented programming and .NET. Check out his upcoming book Professional DevExpress ASP.NET Controls (from Wiley) now available on Amazon.com and fine bookstores everywhere. Look for his upcoming book Teach Yourself the ADO.NET Entity Framework in 24 Hours (from Sams). You may contact him for technology questions at pkimmel@softconcepts .com. Paul Kimmel is a Technical Evangelist for Developer Express, Inc, and you can ask him about Developer Express at paulk@devexpress.com and read his DX blog at http:// community.devexpress.com/blogs/paulk.

This article was originally published on Friday Dec 18th 2009
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