MainWindow.xaml.vb

Imports EntityFrameworkIssues.Issues
Imports System
Imports System.Linq.Expressions
Imports DevExpress.Data.Filtering
Imports DevExpress.Xpf.Data
Imports System.Linq
Imports System.Threading.Tasks
Imports System.Data.Entity
Imports DevExpress.Xpf.Grid
Class MainWindow
    Public Sub New()
        InitializeComponent()
        Dim source = New PagedAsyncSource With {
            .ElementType = GetType(Issue),
            .KeyProperty = NameOf(Issue.Id),
            .PageNavigationMode = PageNavigationMode.ArbitraryWithTotalPageCount
        }
        AddHandler source.FetchPage, AddressOf OnFetchPage
        AddHandler source.GetTotalSummaries, AddressOf OnGetTotalSummaries
        grid.ItemsSource = source
        LoadLookupData()
    End Sub

    Private Function MakeFilterExpression(ByVal filter As CriteriaOperator) As Expression(Of Func(Of Issue, Boolean))
        Dim converter = New GridFilterCriteriaToExpressionConverter(Of Issue)()
        Return converter.Convert(filter)
    End Function

    Private Sub OnFetchPage(ByVal sender As Object, ByVal e As FetchPageAsyncEventArgs)
        Const pageTakeCount As Integer = 5
        e.Result = Task.Run(Of FetchRowsResult)(Function()
                                                    Dim context = New IssuesContext()
                                                    Dim queryable = context.Issues.AsNoTracking().SortBy(e.SortOrder, defaultUniqueSortPropertyName:=NameOf(Issue.Id)).Where(MakeFilterExpression(CType(e.Filter, CriteriaOperator)))
                                                    Return queryable.Skip(e.Skip).Take(e.Take * pageTakeCount).ToArray()
                                                End Function)
    End Sub

    Private Sub OnGetTotalSummaries(ByVal sender As Object, ByVal e As GetSummariesAsyncEventArgs)
        e.Result = Task.Run(Function()
                                Dim context = New IssuesContext()
                                Dim queryable = context.Issues.Where(MakeFilterExpression(CType(e.Filter, CriteriaOperator)))
                                Return queryable.GetSummaries(e.Summaries)
                            End Function)
    End Sub

    Private Sub LoadLookupData()
        Dim context = New IssuesContext()
        usersLookup.ItemsSource = context.Users.[Select](Function(user) New With {
            .Id = user.Id,
            .Name = user.FirstName & " " + user.LastName
        }).ToArray()
    End Sub

End Class