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ASP Program to validate email address

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This is a simple ASP Program to validate email address. The IsValidEmail() function checks for a valid email and returns true if the email address is a valid email otherwise it returns false if the email address isn’t proper syntax. The code is well commented and should explain what is happening .

This code checks for @ and a . period sign as well as only acceptable characters. i.e. if a user have entered # or $ sign in his/her email address then this function will return false.

'*******************************************************
'* MYCPLUS Sample Code - https://www.mycplus.com *
'* *
'* This code is made available as a service to our *
'* visitors and is provided strictly for the *
'* purpose of illustration. *
'* *
'* Please direct all inquiries to saqib at mycplus.com *
'*******************************************************

Function IsValidEmail(emailAddress)
'Declare variables
Dim ValidEmail, emailParts, iLoopCounter, emailChar, acceptableChars
ValidEmail = True 'set the default result to True
'acceptableChars are the characters that we will allow in our email
acceptableChars="abcdefghijklmnopqrstuvwxyz.-_@"
'use the Split function to create an array with the @ as the separator
'so if your email was test@tester.com the email would be split into an array
'with the first array element holding "test" and the second "tester.com"
emailParts = Split(emailAddress, "@")
'check to make sure that there is only 1 @ and that there are 2 parts
'remember arrays are zero based
'Using the UBound function will return the highest element in the array
'So if it's a valid email the UBound function will return 1, i.e. 0 start
If UBound(emailParts) <> 1 Then
ValidEmail = false
Else
'Check the length of each part of the email address
'first part can be just one character, 2nd part must be atleast 4
If Len(emailParts(0))<1 OR Len(emailParts(1))<4 Then
ValidEmail = false
End If
'check first character on the left part isn't a "." using Left function
If Left(emailParts(0), 1)="." Then
ValidEmail = false
End If
'check the last & 2nd character from right part using Right function
If Right(emailParts(1), 1) = "." OR Right(emailParts(1), 2) = "." Then
ValidEmail = false
End If
'check that there is a . in the second part of the email address - .com
If InStr(emailParts(1), ".") <= 0 Then ValidEmail = false End If 'check that there shouldn't be a _ in the second part of the email address If InStr(emailParts(1), "_") >0 Then
ValidEmail = false
End If
End If
'loop through each character of email
For iLoopCounter = 1 to Len(emailAddress)
'Use Lcase & Mid functions, Mid function used to return each individual character
'in the email, and then Lcase converts it into lowercase
emailChar = Lcase(Mid(emailAddress, iLoopCounter, 1))
'Check if the emailAddress characters are acceptable
If InStr(acceptableChars, emailChar) = 0 and Not IsNumeric(emailChar) Then
ValidEmail = false
End if
Next
'check if there is 2 . in a row
If InStr(emailAddress, "..") > 0 Then
ValidEmail=false
End If
'check if there is @. in a row
If InStr(emailAddress, "@.") > 0 Then
ValidEmail=false
End If
IsValidEmail=ValidEmail
End function

 

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M. Saqib: Saqib is Master-level Senior Software Engineer with over 14 years of experience in designing and developing large-scale software and web applications. He has more than eight years experience of leading software development teams. Saqib provides consultancy to develop software systems and web services for Fortune 500 companies. He has hands-on experience in C/C++ Java, JavaScript, PHP and .NET Technologies. Saqib owns and write contents on mycplus.com since 2004.
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