HomeController.vb

Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Web.Mvc
Imports System.Web.Script.Serialization
Imports GridViewOptimisticConcurrencyMvc.Models

Namespace GridViewOptimisticConcurrencyMvc.Controllers

    Public Class HomeController
        Inherits Controller

        Private db As CustomerDbContext = New CustomerDbContext()

        Public Function Index() As ActionResult
            Return View()
        End Function

        Public Function GridViewPartial() As ActionResult
            Return PartialView(db.Customers.ToList())
        End Function

        Public Function GridViewPartialAddNew(ByVal customer As Customer) As ActionResult
            Dim model = db.Customers
            If ModelState.IsValid Then
                Try
                    db.Entry(customer).State = Data.Entity.EntityState.Added
                    db.SaveChanges()
                Catch e As Exception
                    ViewData("EditError") = e.Message
                End Try
            Else
                ViewData("EditError") = "Please, correct all errors."
            End If

            Return PartialView("GridViewPartial", db.Customers.ToList())
        End Function

        Public Function GridViewPartialUpdate(ByVal customer As Customer) As ActionResult
            Dim model = db.Customers
            customer.RowVersion = CalculateOldRowVersion(customer.Id)
            If ModelState.IsValid Then
                Try
                    db.Entry(customer).State = Data.Entity.EntityState.Modified
                    db.SaveChanges()
                Catch e As Exception
                    ViewData("EditError") = e.Message
                End Try
            Else
                ViewData("EditError") = "Please, correct all errors."
            End If

            Return PartialView("GridViewPartial", db.Customers.ToList())
        End Function

        Public Function GridViewPartialDelete(ByVal customer As Customer) As ActionResult
            Dim model = db.Customers
            customer.RowVersion = CalculateOldRowVersion(customer.Id)
            If ModelState.IsValid Then
                Try
                    db.Entry(customer).State = Data.Entity.EntityState.Deleted
                    db.SaveChanges()
                Catch e As Exception
                    ViewData("EditError") = e.Message
                End Try
            Else
                ViewData("EditError") = "Please, correct all errors."
            End If

            Return PartialView("GridViewPartial", db.Customers.ToList())
        End Function

        Private Function CalculateOldRowVersion(ByVal id As Integer) As Byte()
            Dim serializer As JavaScriptSerializer = New JavaScriptSerializer()
            Dim rowVersions As String = Request("RowVersions")
            Dim dictionary As Dictionary(Of Object, String) = CType(serializer.Deserialize(rowVersions, GetType(Dictionary(Of Object, String))), Dictionary(Of Object, String))
            Dim rowVersion As Char() = dictionary(id.ToString()).ToCharArray()
            Return Convert.FromBase64CharArray(rowVersion, 0, rowVersion.Length)
        End Function
    End Class
End Namespace