Append domain name to email for editorFor

Question

I am using C#, MVC4 to build an account class that has a property called GmailAccount, which will be entered by the user.

In Model, I am using the following RegularExpression attribute:

 [RegularExpression(@"[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@gmail.com"] 

This validates the email ends in @gmail.com.

In my html view, I am simply using:

 editorFor(model => model.GmailAccount) @@gmail.com

Note that I have typed in @@gmail in the html to save the user from typing in the domain name, and to ensure/enforce that user uses a valid gmail account.

However, we also note that the same RegularExpression attribute is validated on both the client and the server side. I really don't want my user to type in the domain name manually since I won't allow it to be different from "@gmail.com".

Question:

Is there a way to append @gmail.com to whatever the user provided in editorFor as the user name before both client side and server side validation? Or some other good alternatives?

Answer 1

What I would do is create a view model around what you are trying to do:

public EmailEntryViewModel
{
  private string _emailPrefix = string.Empty;

  public string FullEmailAddress
  {
    get
    {
      return _emailPrefix + "@gmail.com";
    }
    set
    {
      if (!value.EndsWith("@gmail.com", StringComparison.OrdinalIgnoreCase))
      {
        //whatever logic that is internal
        throw new InvalidOperationException("Database contains an invalid email.");
      }

      this._emailPrefix = value.Substring(0,
        email.IndexOf("@gmail.com",  StringComparison.OrdinalIgnoreCase));
    }
  }

 [RegularExpression(@"[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*"]
  public string EmailPrefix
  {
    get 
    {
      return _emailPrefix;
    } 
    set 
    {
      _emailPrefix = value;
    } 
  }
}

Then you only need to:

@Html.EditorFor(model => model.EmailPrefix) @@gmail.com