MSDN Magazine - April 2008 - (Page 27)

ing My.Computer.Network, and customizing the way My.Settings stores application configuration information. What about objects such as My.WebServices and My.Forms? The classes of these objects are nested types defined in Modules, which means they cannot be used with the Partial Class feature, and they are NotInheritable, which means they cannot be extended like My.User. There is no easy way to add members to them. In this case, you must find a better way for your extension to fit into the My namespace. Coding the Extension Now that I’ve explained extensions to the My namespace, let’s see how you can easily implement and share these extensions in our projects. I just showed how My is a namespace like any other namespace, and you can add top-level properties to it by simply adding a module and specifying a namespace of My. Let’s now create a set of validation functions that can check if a string matches the format of U.S. and Canadian postal codes, phone numbers, email addresses, and a few other important formats. Let’s begin by starting Visual Studio® and creating a new console application. Name the project MyValidation. Next, add a new Module to the solution called MyValidation.vb and replace the code in the MyValidation.vb file with the code shown in Figure 5 (which has been excerpted here for space). Figure 5 Validation Code Excerpt Imports Imports Imports Imports System.Text.RegularExpressions System System.Linq Microsoft.VisualBasic Be careful when creating a My Extension template that your code can work in any project configuration. You need to pay particular attention to the possible values of Option Explicit, Option Strict, Option Compare, and (new in Visual Basic 2008) Option Infer. You can either write code that will work in the least-flexible configuration (Option Explicit On, Option Strict On, Option It’s a hassle to re-export your Infer Off, and Option Comextension when you find a pare unspecified), or specify bug, so make the extension each option explicitly at the top of each code file in your as functional as possible extension, which is the recand make sure it’s properly ommended approach. tested before you export it Also, you need to be carefor the first time. ful to account for different project imports to prevent conflict with symbols defined in the project. You do this by qualifying any symbol not defined in your template with the Global or the My keyword. For instance, instead of Text.Encoding, use Global.System.Text.Encoding. If you only use Text.Encoding, your template will not work in Windows® Forms Applications, which imports two namespaces that contain a namespace called Text. If you omit Global and only use System.Text.Encoding, then your template may not work in a project that defines a namespace called System. Namespace My.Validation _ Public Module MyValidationMod Public Function IsEmpty(ByVal value As Object) As Boolean If (value Is Nothing) OrElse _ (value Is System.DBNull.Value) OrElse _ (value.ToString = String.Empty) OrElse _ (TypeOf value Is Date AndAlso CDate(value) = Date.MinValue) _ Then Return True Else Return False End If End Function Public Function IsAlphaNumeric(ByVal value As String, _ Optional ByVal emptyOK As Boolean = False, Optional ByVal _ whitespaceOK As Boolean = False) As Boolean If IsEmpty(value) Then Return emptyOK Dim expr As String If whitespaceOK Then expr = “^[a-zA-Z0-9\s]+$” Else expr = “^[a-zA-Z0-9]+$” End If Return Regex.IsMatch(value, expr) End Function Public Function IsCanadianProvince(ByVal st As String) As Boolean Dim allProv = “|AB|BC|MB|NB|NL|NT|NS|NU|ON|PE|QC|SK|YT” Return st.Length = 2 AndAlso allProv.IndexOf(“|” & st) -1 End Function Public Function IsUSAState(ByRef st As String) As Boolean Dim allStates = “|AL|AK|AZ|AR|CA|CO|CT|DE|FL|GA|HI|ID|IL|IN|IA|” & _ “KS|KY|LA|ME|MD|MA|MI|MN|MS|MO|MT|NE|NV|NH|NJ|NM|NY|NC|ND|OH|” & _ “OK|OR|PA|RI|SC|SD|TN|TX|UT|VT|VA|WA|WV|WI|WY” Return st.Length = 2 AndAlso allStates.IndexOf(“|” & st) -1 End Function Public Function IsUSAPostalCode(ByVal zip As String) As Boolean If String.IsNullOrEmpty(zip) Then Return False Return Regex.IsMatch(zip, “^\d{5}(-\d{4})?$”) End Function Public Function IsCanadianPostalCode(ByVal zip As String) As Boolean If String.IsNullOrEmpty(zip) Then Return False Return Regex.IsMatch(zip, “^[A-Z]\d[A-Z] \d[A-Z]\d$”) End Function Public Function IsNorthAmericanPhone(ByRef phone As String) As Boolean If String.IsNullOrEmpty(phone) Then Return False Dim expr As String = “^(?:$[2-9]\d{2}$\ ?|[2-9]\d{2}” & _ “(?:\-?|\ ?))[2-9]\d{2}[- ]?\d{4}$” Return Regex.IsMatch(phone, expr) End Function Public Function IsEmail(ByRef email As String) As Boolean If String.IsNullOrEmpty(email) Then Return False Dim localPartCharset = “[0-9a-zA-Z!#$%*/?|\^{}`~&’+\-=_]” Dim domainPartCharset = “[0-9a-zA-Z\-]” Dim expr = String.Format(“^{0}+(\.{0}+)*@{1}+(\.{1}+)*”, _ localPartCharset, domainPartCharset) Return Regex.IsMatch(email, expr) End Function End Module End Namespace Basic Instincts april2008 27

Table of Contents Feed for the Digital Edition of MSDN Magazine - April 2008

MSDN Magazine - April 2008 Contents Toolbox CLR Inside Out Basic Instincts Cutting Edge Foundations Test Run Service Station Windows with C++ Going Places { End Bracket }

MSDN Magazine - April 2008

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