Question

I’ve built a UserRepository interface to communicate with my LINQ to SQL Data layer, but I’m trying to figure out how to implement validation.

Here is what my AddUser subroutine looks like

Public Sub AddUser(ByVal about As String, ByVal birthdate As DateTime, ByVal openid As String, ByVal regionid As Integer, ByVal website As String) Implements IUserRepository.AddUser
    Dim user = New User
    user.About = about
    user.BirthDate = birthdate
    user.LastSeen = DateTime.Now
    user.MemberSince = DateTime.Now
    user.OpenID = openid
    user.RegionID = regionid
    user.UserName = String.Empty
    user.WebSite = website

    dc.Users.InsertOnSubmit(user)
    dc.SubmitChanges()
End Sub

And then my controller will simply call AddUser(...)

But I haven’t the foggiest idea on how to implement both client side and server side validation on this.
(I think I would prefer to use jQuery AJAX and do all of the validation on the server, but I’m totally open to opinions)

EDIT:

@vijaysylvester‘s answer was perfect, I just thought I would show a code example of how I implemented it.

UserService.vb

Imports System.ComponentModel.DataAnnotations

Namespace Domain

    <MetadataType(GetType(UserMetaData))> _
    Partial Public Class User : End Class

    Public Class UserMetaData

        <Required(ErrorMessage:="Username is required.")> _
        <StringLength(30, ErrorMessage:="Username cannot exceed 30 characters.")> _
        Public UserName As String

        <StringLength(50, ErrorMessage:="Email Address cannot exceed 50 characters.")> _
        <RegularExpression("^[a-z0-9_\\+-]+(\\.[a-z0-9_\\+-]+)*@[a-z0-9-]+(\\.[a-z0-9+)*\\.([a-z]{2,4})$", ErrorMessage:="Not a valid email address.")> _
        Public Email As String

        <StringLength(256, ErrorMessage:="Web Address cannot exceed 256 characters.")> _
        Public WebSite As String

        <StringLength(4000, ErrorMessage:="Profile cannot exceed 4000 characters.")> _
        Public About As String

    End Class

#Region "Interface"
    Public Interface IUserService
        Sub UpdateUser(ByVal id As Integer, ByVal about As String, ByVal birthdate As DateTime, ByVal openid As String, ByVal regionid As Integer, ByVal username As String, ByVal website As String)
        Sub UpdateUserReputation(ByVal id As Integer, ByVal AmountOfReputation As Integer)
        Sub CloseUser(ByVal id As Integer)
        Sub OpenUser(ByVal id As Integer)
        Function GetAllUsers() As IList(Of User)
        Function GetUserByID(ByVal id As Integer) As User
    End Interface
#End Region


#Region "Service"
    Public Class UserService : Implements IUserService

        Private _UserRepository As IUserRepository

        Public Sub New(ByVal UserRepository As IUserRepository)
            _UserRepository = UserRepository
        End Sub

        Public Sub UpdateUser(ByVal id As Integer, ByVal about As String, ByVal birthdate As Date, ByVal openid As String, ByVal regionid As Integer, ByVal username As String, ByVal website As String) Implements IUserService.UpdateUser
            Dim user = _UserRepository.GetUserByID(id)
            user.About = about
            user.BirthDate = birthdate
            user.RegionID = regionid
            user.UserName = username
            user.WebSite = website

            _UserRepository.UpdateUser(user)
        End Sub

        ''# And the rest of my methods.
    End Class
End Namespace

Answer 1

Though it is meaningful to do validations in server side and client side manually , I would say one can go with open source validation Frameworks such as XVal .

Check out the link below.

XVal reference

It is as easy as just configuring the properties that needs to be validated.

E.g.,

[Required] [StringLength(50)] public string Name { get; set; }

The code snippet above checks if Name is a valid string and its size is not more than 50.

There are numerous built in validators (including Regular Expressions) , which we can make use of for different data types such as Date.

Hope this helps.

Thanks ,
Vijay.