asp.net:使用c#指定MembershipCreateStatus.ProviderError的错误

也许这个问题听起来很傻。在上面的陈述中，谁是提供者？是程序员提供了所需的错误，是用户创建了成员资格，还是其他人？具体来说，当用户键入的字符超过maxlength时，我想显示错误，如下所示：ps。在geterrormessage方法中查找带*的行。。。

UsernameTextbox.MaxLength = 15;
    if (UsernameTextbox.Text.Length > UsernameTextbox.MaxLength)
    {
        status = MembershipCreateStatus.ProviderError;
        Msg.Text = GetErrorMessage(status);
    }

public string GetErrorMessage(MembershipCreateStatus status)
{
   switch (status)
  {

  case MembershipCreateStatus.DuplicateUserName:
    return "Username already exists. Please enter a different user name.";

  case MembershipCreateStatus.DuplicateEmail:
    return "A username for that e-mail address already exists. Please enter a different e-mail address.";
  case MembershipCreateStatus.InvalidPassword:
    return "The password provided is invalid. Please enter a valid password value.";
  case MembershipCreateStatus.InvalidEmail:
    return "The e-mail address provided is invalid. Please check the value and try again.";
  case MembershipCreateStatus.InvalidAnswer:
    return "The password retrieval answer provided is invalid. Please check the value and try again.";
  case MembershipCreateStatus.InvalidQuestion:
    return "The password retrieval question provided is invalid. Please check the value and try again.";
  case MembershipCreateStatus.InvalidUserName:
    return "The user name provided is invalid. Please check the value and try again.";
   //****** STAR LINE:i want to show the following message but i don't know if the-->
  //-->the provider error method can let me do this
  case MembershipCreateStatus.ProviderError:
    return "field outreached the maximum length of characters which is:";
  case MembershipCreateStatus.UserRejected:
    return "The user creation request has been canceled. Please verify your entry and try again. If the problem persists, please contact your system administrator.";
  default:
    return "An unknown error occurred. Please verify your entry and try again. If the problem persists, please contact your system administrator.";
   }
 }