Archives

Archives / 2003 / September

  • Issues with a lambda expression

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    In javascript you can use a function to as an argument to the string.replace function when matching against a regex pattern - this is often referred to as a lambda expression.  For example, in the following piece of code, the function is invoked for each match.  The result is that the letters in the word "foo" are alerted in sequence:

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  • Windows Authentication with Role based authorization

    6 Comments

    I've done a fair bit with ASP.NET security using the FormsAuthentication provider but not much at all with Windows authentication.  I'm currently building an app. “out-of-hours” that needed to use integrated Windows authentication and also use Role based authorization based on the users Windows Group membership.  Here is a little piece of code that I put together to hook the Windows groups into the roles of the IPrincipal in the application:

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  • Application.DoStuff

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    I nice little post by Eric Gunnerson that talked how to add an odd-shaped splash screen to an application.  The most interesting thing that came out of this post for me was that he mentioned having to call Application.DoEvents to allow Windows to process the necessary messages to get the splash form to render properly.  Being a web-guy Application.DoEvents is something that I've never really come to terms with.  If you were to go under the hood of some of my winforms apps you would undoubtedly uncover a shot-gun approach to calling this method - i.e.:  sprayed at random.

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  • Regex Reminders [1] - Replacement Operations

    11 Comments

    A common application for regular expressions is to find and replace strings within a body of text. These operations range from something as simple as finding some text and removing it to locating and re-writing Hmtl tags. Let's take a quick look at the signatures of the .NET Regular Expression Replace overloads.

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  • Regex Reminders #0 - Commenting Regular Expressions

    10 Comments 

    Free spacing and comment mode
    .NET Regular Expressions allow you to embed comments and whitespace within pattern strings making them clearer to 
    read (because of the whitespace), and easier to maintain (due to the modularity).

To use this feature you must turn on the RegexOptions.IgnorePatternWhitespace flag.  This can be achieved 
    either by using the RegexOptions enumerated datatype or, via the (?x) mode modifier.  Therefore the following 
    two examples are functionally identical:


    Regex re = new Regex( 
        @"           # This pattern matches Foo
            (?i)     # turn on insensitivity
                     # The Foo bit
            \b(Foo)\b "
        , RegexOptions.IgnorePatternWhitespace ) ;


    Regex re = new Regex( 
        @"(?x)
                    # This pattern matches Foo
            (?i)    # turn on insensitivity
                    # The Foo bit
            \b(Foo)\b "
        ) ;


Using IgnorePatternWhitespace option, comments can be embedded in one of two ways.  Firstly, a raw '#' 
    character can be used to mark the beginning of a comment and the comment runs up to the first NEWLINE 
    (\n) character that is encountered.  This can be easily achieved in C# with verbatim strings @"..." 
    or in VB by appending newline characters within the string using Chr(10), vbCrLf or Environment.NewLine.  
    Comments can also be declared using the (?#...) syntax.

The following 3 snippets demonstrate examples of each of these methods...


C# Verbatim Strings.


    using System;
    using System.Collections;
    using System.Text.RegularExpressions ;

    namespace Regex Snippets.Tests
    {
        public class CommentedCSharp
        {
            public static void Main()
            {
                Regex re = new Regex( 
                    @"           # This pattern matches Foo
                        (?i)     # turn on insensitivity
                                 # The Foo bit
                        \b(Foo)\b "
                , RegexOptions.IgnorePatternWhitespace ) ;
        
                for ( Match m = re.Match( "foo bar Foo" ) ; m.Success ; m = m.NextMatch() )
                    Console.WriteLine( m.Value + Environment.NewLine ) ;
                
                Console.ReadLine();
            }
        }    
    }



VB.NET using (?#...) syntax.


    Option Strict On

    Imports System.Text.RegularExpressions


    Namespace Regex Snippets.Tests

        Module CommentedVBOne

            Public Sub Main()

                ' Demonstrates a VB Whitespace pattern using the 
                '" (?#...) " & _
                ' syntax
                Dim re As New Regex( _
                        "                   (?# This pattern matches Foo ) " & _
                        "  (?i)             (?# turn on insensitivity ) " & _
                        "                   (?# The Foo bit ) " & _
                        "  \b(Foo)\b " _
                    , RegexOptions.IgnorePatternWhitespace)

                Dim m As Match = re.Match("foo bar foo")
                Dim s As String = ""

                While m.Success
                    s &= (m.Value & Environment.NewLine)
                    m = m.NextMatch()
                End While
                MessageBox.Show(s)
            End Sub

        End Module

    End Namespace



VB.NET using appended newlines.


Option Strict On

    Imports System.Text.RegularExpressions


    Namespace Regex Snippets.Tests

        Module CommentedVBTwo

            Public Sub Main()

                ' Demonstrates a VB Whitespace pattern using the 
                '" (?#...) " & _
                ' syntax
                Dim re As New Regex( _
                        "                 # This pattern matches Foo " & vbCrLf & _
                        "  (?i)           # turn on insensitivity " & vbCrLf & _
                        "                 # The Foo bit " & vbCrLf & _
                        "  \b(Foo)\b " _
                        , RegexOptions.IgnorePatternWhitespace)

                Dim m As Match = re.Match("foo bar foo")
                Dim s As String = ""

                While m.Success
                    s &= (m.Value & Environment.NewLine)
                    m = m.NextMatch()
                End While
                MessageBox.Show(s)
            End Sub

        End Module

    End Namespace

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  • Regex Reminders - A brief explanation

    1 Comment

    Over the next couple weeks I'm going to post a series of regular expression examinations; each one will be a code intensive focus on a certain operations such as "Replace" or "Working with Matches and Groups".  The goal of the Regex Reminders is to end up with a lot of code for working with regex's that people can just use to "grab and go".  The series will also spend time looking at common regex techniques such as alternation and grouping techniques.

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  • Redefining Boundaries - \b and \B

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    \b and \B are useful metacharacters; they provide a simple syntax to easily find items that exist around word boundaries (or, in the case of \B, non-word boundaries).  For example, to find the word "per" you can wrap the actual text inside \b's to ensure that the phrase is not inadvertantly matched when found inside of "person" or "Supercalif", i.e.:

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  • MarkItUp.WebControls.Timer

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    I've finally finished my first server control that is targetted as a public release.  The control is a Timer control that generates optional client-side events and performs a server postback after a specified duration.

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  • \G - match at the end of the previous match.

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    Over the next few days I'd like to spend a bit of time looking at using \G in the .NET "flavour" of regular expressions.  I'd love to hear from anyone that has *had* to use \G in a real-world application (.NET only).

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  • KPI ServerControl Source

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    Option Strict On


Imports System
Imports System.ComponentModel
Imports System.Configuration
Imports System.Data
Imports System.Drawing
Imports System.Web.UI
Imports System.Web.UI.WebControls



'*********************************************************************
'
' KPIs Class
'
' WebControl that displays a listing of KPIs for a given Category/Month. 
'
'*********************************************************************

< _
 Description("WebControl that displays a listing of KPIs for a given Category/Month."), _
 DefaultProperty("DataSource"), _
 Designer(GetType(KPIsDesigner)), _
 ToolboxData("<{0}:KPIs runat=server></{0}:KPIs>") _
> _
Public Class KPIs
    Inherits Web.UI.WebControls.Table
    Implements INamingContainer

    Private mstrCategoryName As String = String.Empty
    Private mstrNavigateUrl As String = String.Empty
    Private mstrBaseImagePath As String = String.Empty
    Private mdtmSelectedMonth As DateTime = DateTime.MinValue
    Private mDatasource As DataTable

    '*********************************************************************
    '
    ' BaseImagePath Property
    '
    ' The directory to look in to find the images.
    '
    '*********************************************************************
    < _
        Browsable(True), _
        Description("The directory to look in to find the images."), _
        Category("Data") _
    > _
    Public Property BaseImagePath() As String
        Get
            Return Me.mstrBaseImagePath
        End Get
        Set(ByVal Value As String)
            Me.mstrBaseImagePath = Value
        End Set
    End Property


    '*********************************************************************
    '
    ' CategoryName Property
    '
    ' The CategoryName to filterBy.
    '
    '*********************************************************************
    < _
        Browsable(True), _
        Description("The name of the current category being displayed."), _
        Category("Data") _
    > _
    Public Property CategoryName() As String
        Get
            Return Me.mstrCategoryName
        End Get
        Set(ByVal Value As String)
            Me.mstrCategoryName = Value
        End Set
    End Property


    < _
        Browsable(True), _
        Description("The foreground color for alternating items in the table."), _
        Category("Appearance") _
    > _
    Public Property AlternatingForeColor() As Color
        Get
            If ViewState("AlternatingForeColor") Is Nothing Then
                Return Me.ForeColor
            Else
                Return CType(ViewState("AlternatingForeColor"), Color)
            End If
        End Get
        Set(ByVal Value As Color)
            ViewState("AlternatingForeColor") = Value
        End Set
    End Property


    < _
        Browsable(True), _
        Description("The background color for alternating items in the table."), _
        Category("Appearance") _
    > _
    Public Property AlternatingBackColor() As Color
        Get
            If ViewState("AlternatingBackColor") Is Nothing Then
                Return Me.ForeColor
            Else
                Return CType(ViewState("AlternatingBackColor"), Color)
            End If
        End Get
        Set(ByVal Value As Color)
            ViewState("AlternatingBackColor") = Value
        End Set
    End Property


    < _
        Browsable(True), _
        Description("The DataTable to use as a datasource."), _
        Category("Data") _
    > _
    Public Property DataSource() As DataTable
        Get
            Return Me.mDatasource
        End Get
        Set(ByVal Value As DataTable)
            Me.mDatasource = Value
        End Set
    End Property




    '*********************************************************************
    '
    ' NavigateUrl Property
    '
    ' The Url to navigate to to display the details for a given KPI
    '
    '*********************************************************************
    < _
        Browsable(True), _
        Description("The Url to navigate to to display the details for a given KPI.  Uses a {0} placeholder to insert the Id of the KPI."), _
        Category("Data") _
    > _
    Public Property NavigateUrl() As String
        Get
            Return Me.mstrNavigateUrl
        End Get
        Set(ByVal Value As String)
            Me.mstrNavigateUrl = Value
        End Set
    End Property


    '*********************************************************************
    '
    ' Controls Property
    '
    ' Make sure that when you access a child control, the
    ' CreateChildControls method has been called.
    '
    '*********************************************************************
    Public Overrides ReadOnly Property Controls() As ControlCollection
        Get
            EnsureChildControls()
            Return MyBase.Controls
        End Get
    End Property


    '*********************************************************************
    '
    ' SelectedMonth Property
    '
    ' The SelectedMonth to filterBy.
    '
    '*********************************************************************
    < _
        Browsable(True), _
        Description("The resultset is filtered by the Month of the DateTime that is passed in."), _
        Category("Data") _
    > _
    Public Property SelectedMonth() As DateTime
        Get
            Return Me.mdtmSelectedMonth
        End Get
        Set(ByVal Value As DateTime)
            Me.mdtmSelectedMonth = Value
        End Set
    End Property



    Protected Overrides Sub CreateChildControls()
        Controls.Clear()

        If mDatasource Is Nothing Then
            mDatasource = GetData()
        End If

        If Not mDatasource Is Nothing Then
            Me.Rows.Add(BuildHeaderRow())

            For Each row As DataRow In mDatasource.Rows
                Dim KPIId As Integer = Convert.ToInt32(row.Item("kpiId"))
                Dim KPIDescription As String = row.Item("kpiDescription").ToString

                Dim mtdRaw As Double = Convert.ToDouble(row.Item("mtdRawValue"))
                Dim ytdRaw As Double = Convert.ToDouble(row.Item("ytdRawValue"))
                Dim mtdDisplay As Integer = Convert.ToInt32(row.Item("mtdDisplayFlag"))
                Dim ytdDisplay As Integer = Convert.ToInt32(row.Item("ytdDisplayFlag"))

                Dim alternating As Boolean = (Me.Rows.Count Mod 2 = 0)
                Me.Rows.Add(BuildRow(KPIId, KPIDescription, mtdRaw, ytdRaw, mtdDisplay, ytdDisplay, alternating))
            Next
        End If
    End Sub


    '*********************************************************************
    '
    ' Render Method
    '
    '*********************************************************************
    Protected Overrides Sub Render(ByVal tw As HtmlTextWriter)
        MyBase.Render(tw)
    End Sub ' Render


    Private Function BuildRow(ByVal kpiId As Integer, ByVal kpiDescription As String, ByVal mtdRaw As Double, _
            ByVal ytdRaw As Double, ByVal mtdDisplay As Integer, ByVal ytdDisplay As Integer, ByVal isAlternatingItem As Boolean) As TableRow
        Dim cell As TableCell
        Dim row As New TableRow

        If isAlternatingItem Then
            row.ForeColor = Me.AlternatingForeColor
            row.BackColor = Me.AlternatingBackColor
        End If

        Dim link As New HyperLink
        link.Text = kpiDescription
        If Not Me.mstrNavigateUrl Is String.Empty Then
            link.NavigateUrl = String.Format(Me.NavigateUrl, kpiId)
        End If

        cell = New TableCell
        cell.Controls.Add(link)
        row.Cells.Add(cell)


        cell = New TableCell
        cell.Controls.Add(GetImage(mtdDisplay, mtdRaw, "MTD"))
        row.Cells.Add(cell)


        cell = New TableCell
        cell.Controls.Add(GetImage(ytdDisplay, ytdRaw, "YTD"))
        row.Cells.Add(cell)

        Return row
    End Function


    Private Function BuildHeaderRow() As TableRow
        Dim cell As TableCell
        Dim row As New TableRow

        cell = New TableHeaderCell
        cell.Text = "&nbsp;"
        row.Cells.Add(cell)

        cell = New TableHeaderCell
        cell.Text = "MTD"
        row.Cells.Add(cell)

        cell = New TableHeaderCell
        cell.Text = "YTD"
        row.Cells.Add(cell)

        Return row
    End Function


    Private Function GetData() As DataTable
        Return Nothing
    End Function


    '*********************************************************************
    '
    ' GetImage Method
    '
    ' Returns the appropriate image for a particular rating.
    '
    '*********************************************************************
    Friend Function GetImage(ByVal ratingNumber As Integer, ByVal rawVal As Double, ByVal desc As String) As Web.UI.WebControls.Image
        Dim img As New Web.UI.WebControls.Image

        If Me.mstrBaseImagePath <> String.Empty Then
            If ratingNumber = 1 Then
                img.ImageUrl = Page.ResolveUrl(String.Format("{0}/Green.gif", Me.mstrBaseImagePath))
            ElseIf ratingNumber = 2 Then
                img.ImageUrl = Page.ResolveUrl(String.Format("{0}/Yellow.gif", Me.mstrBaseImagePath))
            ElseIf ratingNumber = 3 Then
                img.ImageUrl = Page.ResolveUrl(String.Format("{0}/Red.gif", Me.mstrBaseImagePath))
            Else
                img.ImageUrl = Page.ResolveUrl(String.Format("{0}/Spacer.gif", Me.mstrBaseImagePath))
            End If
        End If

        img.AlternateText = String.Format("{1} : {0}", rawVal, desc)
        Return img
    End Function 'GetImage 


End Class

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  • using C# and unlocking some secrets

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    Recently, I've made a decision that all of the code that I write "out of hours" (which is most of the code that I write these days) will be written in C#; and what I'm finding is that switching languages is a very tricky affair.  There's so many little pieces of the language that you have to get used to.  Take the using statement - as opposed to the using directive - for example.  At first sight it seems interesting, according to the docco. it allows me to use an IDisposable type and the call to dispose will get handled under the covers; GREAT!  Or is it?  First of all, methinks that, by the very nature of IDisposable, anything that implemented that interface would be worth putting in a try{}catch{} because you are relying on an "external" resource being available!  So it appears that a statement such as:

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  • Conditional matching

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    Today, while proving what a prat I am, I added some conditional testing to a pattern which I had written.  Conditional matching allows you to perform a test based on if...then[...else] logic.  The syntax is (?if then | else ) - with the 'else' part being optional.

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  • Good VBScript reference

    2 Comments

    I never really did much VB6 programming - built a couple of insignificant apps but that was about it - and today a friend asked me to package some VBScript routines into an ActiveX Library project.  It all went pretty well except for the fact that I couldn't work out which .dll to reference to get the VBScript ESCAPE and UNESCAPE functions in my VB6 code.  While looking around Msdn for version numbers etc. I came across this neat little VBScript reference:

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  • Using backreferences in a Match

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    You can reference backreferences within a regular expression to keep the length and complexity of patterns to a minimum.  Backreferences can be referenced with the \1..\N or \k'name' notation.  To highlight where this is useful consider a simple-minded pattern for matching Dates.  Dates can (potentially) be delimited by either a space, a dot, a hyphen or a slash - that is, any of the following might be allowed:

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  • Find words NOT IN text

    1 Comment

    I'm currently writing a series of articles (that will hopefully get published {grin}) titled "Regex Reminders" that will provide dozens of code snippets that demonstrate how to perform common - and some not-so-common - operations using regex.

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  • Date Regex - [ Note To Self ]

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    While scouring through the pile of comments that have been left on RegexLib.com I noticed a pattern which purports to validate Dates in dmy format.  I couldn't help but notice that all of the comments which have been left have been highly favourable of this expression.

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