VB.Net Regular Expressions

Replace

      Private Function Regex_Replace(textIn As String, reg As String, replaceWith As String) As String
        ' This function examines textIn and replaces all matches of the regularexpression... reg
        Dim regularEx As Text.RegularExpressions.Regex = New Text.RegularExpressions.Regex(reg)
        Dim txt As String
        txt = regularEx.Replace(textIn, replaceWith)
        Return txt
    End Function

Contains

    Private Function Regex_IsPresent(textToSearch As String, reg As String) As Boolean
        Dim regularEx As Text.RegularExpressions.Regex = New Text.RegularExpressions.Regex(reg)
        Dim mat As Text.RegularExpressions.Match = regularEx.Match(textToSearch)
        Return mat.Success
    End Function

Find in String

    Private Function Regex_Find(textToSearch As String, reg As String) As Integer
        ' will return -1 if no match
        ' will return 0 based index showing position of first match if found
        Dim regularEx As Text.RegularExpressions.Regex = New Text.RegularExpressions.Regex(reg)
        Dim mat As Text.RegularExpressions.Match = regularEx.Match(textToSearch)
        If mat.Success Then
            Return mat.Index
        End If
        Return -1
    End Function

Regular Expressions are very powerful search/replace tools and there are complete books dedicated to their use. Whilst there are too many variations to cover in one web page, I have included a sumary of some popular codes. (For simplicity I have assumed the regex is being applied to a string that is only one line in length (i.e. no embedded line feeds)

Valid Date

\t      Matches a tab
\r      Matches a carriage return
[abc]   Matches any character in box (case-sensitive)
[^    ] Matches any character that is not in box
[a-z]   Matches any character in the range a to z
. 	Matches any character except newline
\d      Matches any decimal digit (same as [0-9])
\D 	Matches any character that is not a decimal digit (same as [^0-9])
^       (When not in box) Only matches if match starts in first character of string
$       Only matches if match ends at last character of string
\G      Only matches if match occurs at the same position that the last match ended
* 	Matches previous secrion zero or more times
+ 	Matches the previous section one or more times
? 	Matches the previous section zero or one time
{5} 	Matches the previous element exactly 5 times
{6,} 	Matches the previous element at least 6 times
{7,9} 	Matches the previous element between 7 times and 9 times
? 	(If following {...} * + or ?) Match the minimum number of times to obey any other regex requirements

Is Plausible UK Postcode

(GIR 0AA|[A-PR-UWYZ]([0-9]{1,2}|([A-HK-Y][0-9]|[A-HK-Y][0-9]([0-9]|[ABEHMNPRV-Y]))|[0-9][A-HJKPS-UW]) [0-9][ABD-HJLNP-UW-Z]{2})

Is Plausible UK National Insurance

^(?!BG)(?!GB)(?!NK)(?!KN)(?!TN)(?!NT)(?!ZZ)(?:[A-CEGHJ-PR-TW-Z][A-CEGHJ-NPR-TW-Z])(?:\s*\d\s*){6}([A-D]|\s)$

Is Plausible Email

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])

Is Plausible UK Driving Licence Number

[A-Z0-9]{5}\d[0156]\d([0][1-9]|[12]\d|3[01])\d[A-Z0-9]{3}[A-Z]{2}

The code functions on this site are only intended as a learning aid. Data validation is often ommited to assist users unfamiliar with Visual Basic. The information may be untested, unrelaible or unsuitable for your requiremensts. It is presented in a non-commercial form as an ex-gratia attempt to be helpful. By making any use of information contained on these pages, you agree to fully absolve and indemnify DigitalDan in relation to any issue arising out of such use.