How do I validate email address formatting with the .NET Framework?

Question

I want a function to test that a string is formatted like an email address.

What comes built-in with the .NET framework to do this?

This works:

Answer 1

Another function to check that the email is valid or not :

Public Function ValidEmail(ByVal strCheck As String) As Boolean
    Try
        Dim bCK As Boolean
        Dim strDomainType As String
        Const sInvalidChars As String = "!#$%^&*()=+{}[]|\;:'/?>,< "
        Dim i As Integer
        'Check to see if there is a double quote
        bCK = Not InStr(1, strCheck, Chr(34)) > 0
        If Not bCK Then GoTo ExitFunction
        'Check to see if there are consecutive dots
        bCK = Not InStr(1, strCheck, "..") > 0
        If Not bCK Then GoTo ExitFunction
        ' Check for invalid characters.
        If Len(strCheck) > Len(sInvalidChars) Then
            For i = 1 To Len(sInvalidChars)
                If InStr(strCheck, Mid(sInvalidChars, i, 1)) > 0 Then
                    bCK = False
                    GoTo ExitFunction
                End If
            Next
        Else
            For i = 1 To Len(strCheck)
                If InStr(sInvalidChars, Mid(strCheck, i, 1)) > 0 Then
                    bCK = False
                    GoTo ExitFunction
                End If
            Next
        End If

        If InStr(1, strCheck, "@") > 1 Then 'Check for an @ symbol
            bCK = Len(Left(strCheck, InStr(1, strCheck, "@") - 1)) > 0
        Else
            bCK = False
        End If
        If Not bCK Then GoTo ExitFunction
        strCheck = Right(strCheck, Len(strCheck) - InStr(1, strCheck, "@"))
        bCK = Not InStr(1, strCheck, "@") > 0 'Check to see if there are too many @'s
        If Not bCK Then GoTo ExitFunction
        strDomainType = Right(strCheck, Len(strCheck) - InStr(1, strCheck, "."))
        bCK = Len(strDomainType) > 0 And InStr(1, strCheck, ".") < Len(strCheck)
        If Not bCK Then GoTo ExitFunction
        strCheck = Left(strCheck, Len(strCheck) - Len(strDomainType) - 1)
        Do Until InStr(1, strCheck, ".") <= 1
            If Len(strCheck) >= InStr(1, strCheck, ".") Then
                strCheck = Left(strCheck, Len(strCheck) - (InStr(1, strCheck, ".") - 1))
            Else
                bCK = False
                GoTo ExitFunction
            End If
        Loop
        If strCheck = "." Or Len(strCheck) = 0 Then bCK = False
ExitFunction:
        ValidEmail = bCK
    Catch ex As ArgumentException
        Return False
    End Try
    Return ValidEmail
End Function

How to use it:

Private Sub TextBox2_KeyDown(sender As Object, e As KeyEventArgs) Handles TextBox2.KeyDown
    If e.KeyCode = Keys.Enter Then
        If TextBox2.Text = "" Then
            MsgBox("Write Down Your email and Press Enter") : TextBox2.Select()
        Else

            If ValidEmail(TextBox2.Text) Then ' to check if the email is valid or not
                   'do whatever
            Else
                MsgBox("Please Write Valid Email")
                TextBox2.Select()
            End If
        End If
    End If
End Sub

Answer 2

'-----------------------------------------------------------------------

'Creater : Rachitha Madusanka

'http://www.megazoon.com

'jewandara@gmail.com

'jewandara@hotmail.com

'Web Designer and Software Developer

'@ http://www.zionx.net16.net

'-----------------------------------------------------------------------




Function ValidEmail(ByVal strCheck As String) As Boolean
    Try
        Dim bCK As Boolean
        Dim strDomainType As String


        Const sInvalidChars As String = "!#$%^&*()=+{}[]|\;:'/?>,< "
        Dim i As Integer

        'Check to see if there is a double quote
        bCK = Not InStr(1, strCheck, Chr(34)) > 0
        If Not bCK Then GoTo ExitFunction

        'Check to see if there are consecutive dots
        bCK = Not InStr(1, strCheck, "..") > 0
        If Not bCK Then GoTo ExitFunction

        ' Check for invalid characters.
        If Len(strCheck) > Len(sInvalidChars) Then
            For i = 1 To Len(sInvalidChars)
                If InStr(strCheck, Mid(sInvalidChars, i, 1)) > 0 Then
                    bCK = False
                    GoTo ExitFunction
                End If
            Next
        Else
            For i = 1 To Len(strCheck)
                If InStr(sInvalidChars, Mid(strCheck, i, 1)) > 0 Then
                    bCK = False
                    GoTo ExitFunction
                End If
            Next
        End If

        If InStr(1, strCheck, "@") > 1 Then 'Check for an @ symbol
            bCK = Len(Left(strCheck, InStr(1, strCheck, "@") - 1)) > 0
        Else
            bCK = False
        End If
        If Not bCK Then GoTo ExitFunction

        strCheck = Right(strCheck, Len(strCheck) - InStr(1, strCheck, "@"))
        bCK = Not InStr(1, strCheck, "@") > 0 'Check to see if there are too many @'s
        If Not bCK Then GoTo ExitFunction

        strDomainType = Right(strCheck, Len(strCheck) - InStr(1, strCheck, "."))
        bCK = Len(strDomainType) > 0 And InStr(1, strCheck, ".") < Len(strCheck)
        If Not bCK Then GoTo ExitFunction

        strCheck = Left(strCheck, Len(strCheck) - Len(strDomainType) - 1)
        Do Until InStr(1, strCheck, ".") <= 1
            If Len(strCheck) >= InStr(1, strCheck, ".") Then
                strCheck = Left(strCheck, Len(strCheck) - (InStr(1, strCheck, ".") - 1))
            Else
                bCK = False
                GoTo ExitFunction
            End If
        Loop
        If strCheck = "." Or Len(strCheck) = 0 Then bCK = False

ExitFunction:
        ValidEmail = bCK
    Catch ex As ArgumentException
        Return False
    End Try
    Return ValidEmail
End Function

Answer 3

You could use a Regex to do this.

There have been written a lot of articles about it; this came up when I searched google for 'regex to validate email address': Find or Validate an Email Address.

Answer 4

I have tested the approved 'answer' in this case and it does not seem to adhere to the specifications of what actually is a valid email address. After many headaches I found this regex which does a much better job than Microsoft does.

"(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]" +
")+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:" +
"\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(" +
"?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ " +
"\t]))*""(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\0" +
"31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\" +
"](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+" +
"(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:" +
"(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z" +
"|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)" +
"?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\" +
"r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[" +
" \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)" +
"?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t]" +
")*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[" +
" \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*" +
")(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]" +
")+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)" +
"*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+" +
"|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r" +
"\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:" +
"\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t" +
"]))*""(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031" +
"]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](" +
"?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?" +
":(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?" +
":\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?" +
":(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?" +
"[ \t]))*""(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\"".\[\] " +
"\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|" +
"\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>" +
"@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""" +
"(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t]" +
")*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\" +
""".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?" +
":[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[" +
"\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\"".\[\] \000-" +
"\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(" +
"?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;" +
":\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([" +
"^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\""" +
".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\" +
"]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\" +
"[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\" +
"r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] " +
"\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]" +
"|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\"".\[\] \0" +
"00-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\" +
".|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@," +
";:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|""(?" +
":[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*" +
"(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\""." +
"\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[" +
"^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\]" +
"]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*(" +
"?:(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\" +
""".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*)(?:\.(?:(" +
"?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[" +
"\[""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t" +
"])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t" +
"])+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?" +
":\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|" +
"\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:" +
"[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\"".\[\" +
"]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)" +
"?[ \t])*(?:@(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""" +
"()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)" +
"?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>" +
"@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[" +
" \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@," +
";:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t]" +
")*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\" +
""".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?" +
"(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[""()<>@,;:\\""." +
"\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:" +
"\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[" +
"""()<>@,;:\\"".\[\]]))|""(?:[^\""\r\\]|\\.|(?:(?:\r\n)?[ \t]))*""(?:(?:\r\n)?[ \t])" +
"*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])" +
"+|\Z|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\" +
".(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z" +
"|(?=[\[""()<>@,;:\\"".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(" +
"?:\r\n)?[ \t])*))*)?;\s*)"

I have already formatted it as a vb string using a simple application. Too bad stack overflow is more interested in being a 'coding repository' than having the complete answer for the problem.

Answer 5

 Public Shared Function ValidEmailAddress(ByVal emailAddress As String, ByRef errorMessage As String) As Boolean
        If emailAddress.Length = 0 Then
            errorMessage = "E-mail address is required."
            Return False
        End If
        If emailAddress.IndexOf("@") > -1 Then
            If (emailAddress.IndexOf(".", emailAddress.IndexOf("@")) > emailAddress.IndexOf("@")) AndAlso emailAddress.Split(".").Length > 0 AndAlso emailAddress.Split(".")(1) <> "" Then
                errorMessage = ""
                Return True
            End If
        End If
        errorMessage = "E-mail address must be valid e-mail address format."
        Return False
    End Function