Introduction:
This tutorial is on how to make an email addres validator tool in Visual Basic.

Design:
This tool will contain;
a textbox, named defaultly textbox1, this is where the string to be validated will be enetered.
a button, named defaulty button1, this is how the validation process will begin.

Imports:
To validate the string as an email, we are going to be using RegEx which requires it's own import from...

1. Imports System.Text.RegularExpressions
   

RegEx String:
Then on the button1 click we first create a RegEx string to match our string against...

1. Dim
   
   emailRegex As
   
   New
   
   System.Text.RegularExpressions.Regex("^(?<user>[^@]+)@(?<host>.+)$"
   
   )
   

This regex - emailRegex - is an official Microsoft Visual Basic regex to ensure that any strings parsed through this method are properly validated to an email.

The Match:
Now that we have our Regex string to match our string against, we can create a new Regex Match variable - essentially a boolean - which contains whether the parsed string is a match to the earlier created regex - emailRegex - we parse the string entered in to the first textbox - textbox1 - by using the .text property of the textbox1 textbox...

1. Dim
   
   emailMatch As
   
   System.Text.RegularExpressions.Match = emailRegex.Match(TextBox1.Text)
   

Output:
Finally we can output the results. We msgbox "This email is valid." if the entered string is in an email format, or "This is not a valid email" if not...

1. If
   
   (emailMatch.Success) Then
   
2. MsgBox("This email is valid."
   
   )
   
3. Else
   
   : MsgBox("This is not a valid email."
   
   )
   
4. End
   
   If
   

Full Source:
Done. Here is the full source!

1. Imports System.Text.RegularExpressions
   
2. 
   
3. Public
   
   Class Form1
   
4. Private
   
   Sub
   
   Button1_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button1.Click
   
5. Dim
   
   emailRegex As
   
   New
   
   System.Text.RegularExpressions.Regex("^(?<user>[^@]+)@(?<host>.+)$"
   
   )
   
6. Dim
   
   emailMatch As
   
   System.Text.RegularExpressions.Match = emailRegex.Match(TextBox1.Text)
   
7. If
   
   (emailMatch.Success) Then
   
8. MsgBox("This email is valid."
   
   )
   
9. Else
   
   : MsgBox("This is not a valid email."
   
   )
   
10. End
    
    If
    
11. End
    
    Sub
    
12. End
    
    Class