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check whether the @ exists

By Petros
Mar 20, 2006
  1. i am working on a visual basic project and i have the following problem. i use a textbox were users enter their email address. i want to check whether the @ symbol exists in the textbox.
    how can this be done?
     
  2. RealBlackStuff

    RealBlackStuff TS Rookie Posts: 6,503

    ever heard of Google?
    Try "visual basic check for valid email"
     
  3. MrGaribaldi

    MrGaribaldi TechSpot Ambassador Posts: 2,512

    Without knowing (/remembering) anything of VB, the easiest way would be to run through the text string character by character, and check if there is an '@' in there, and that somewhere after it, there is a '.' followed by 2 to 4 characters.
    That will be a better way than most programmes does it, as they usually accept "you@re.stupid" or similar adresses.
    Of course, it takes more cpu cycles, but still..
     
  4. Mictlantecuhtli

    Mictlantecuhtli TS Evangelist Posts: 4,345   +11

    I did this recently in one PHP code I had to do. There are a lot of allowed characters in the address before @ and in the domain after it, it's just that too many e-mail applications aren't designed to handle "international" characters.

    Furthermore, it's not just two to four characters allowed in domain, and I presume you meant a dot instead of a comma. There can be any number of dots in the domain address, as far as I know (zero could be localhost, for example; two are used in many countries, .co.uk, .co.jp etc.). One simple way would be to check if the domain exists in DNS records.

    Besides, top-level domains can have more than four characters, for example http://about.museum is a valid URL.

    See also: RFC822: Standard for ARPA Internet Text Messages
     
  5. MrGaribaldi

    MrGaribaldi TechSpot Ambassador Posts: 2,512

    Ok, I admit it, I'm somewhat tired, and my fingers aren't hitting all the right keys at the right time... Yes, I meant 'dot' not comma.

    As for checking for the dot, I didn't mean there should only be one, I only meant you should check that there is a dot at the end followed by up to a certain amount of characters. But I was wrong about the amount of characters there can be in a top leve domain.

    What could be done is to retrieve a list of top level domains every now and again and compare against that. Checking for if it is a complete valid domain would take some time, and would increase the complexity of the program by quite a bit. Though it is a good idea.

    As for international characters, I know, and I'm pretty pissed off there is so little support. I've got a nice little domain name, but it contains an international character, and since neither IE nor outlook supports that at present, there is no use for it... But in a couple of years, hopefully...
    Anyways I digress...
     
  6. RealBlackStuff

    RealBlackStuff TS Rookie Posts: 6,503

  7. Petros

    Petros TS Rookie Topic Starter

    thanks

    thanks for the tip guys
     
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