Form1.vb

Imports System
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Windows.Forms
Imports DevExpress.XtraEditors
Imports DevExpress.XtraEditors.Controls
Imports DevExpress.XtraEditors.Repository

Namespace NotFoundValue

    Public Partial Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs)
            Dim tblLookUp As DataTable = New DataTable()
            tblLookUp.Columns.Add("Code", GetType(Integer))
            tblLookUp.Columns.Add("Name")
            tblLookUp.Rows.Add(New Object() {1, "one"})
            tblLookUp.Rows.Add(New Object() {2, "two"})
            Dim tblGrid As DataTable = New DataTable()
            tblGrid.Columns.Add("Number", GetType(Integer))
            For i As Integer = 0 To 3 - 1
                tblGrid.Rows.Add(New Object() {i})
            Next

            gridControl1.DataSource = tblGrid
            Dim editor As RepositoryItemLookUpEdit = TryCast(gridControl1.RepositoryItems.Add("LookUpEdit"), RepositoryItemLookUpEdit)
            editor.DataSource = tblLookUp
            editor.ValueMember = "Code"
            editor.DisplayMember = "Name"
            AddHandler editor.CustomDisplayText, New CustomDisplayTextEventHandler(AddressOf RepositoryItemLookUpEdit_CustomDisplayText)
            gridView1.Columns(0).ColumnEdit = editor
            ' add the second column bound to the same field for easier reference
            gridView1.Columns.AddField("Number").VisibleIndex = 1
            lookUpEdit1.Properties.Assign(editor)
            lookUpEdit1.EditValue = 0
        End Sub

        Const NotFoundText As String = "???"

        Private Sub RepositoryItemLookUpEdit_CustomDisplayText(ByVal sender As Object, ByVal e As CustomDisplayTextEventArgs)
            Dim props As RepositoryItemLookUpEdit
            If TypeOf sender Is LookUpEdit Then
                props = TryCast(sender, LookUpEdit).Properties
            Else
                props = TryCast(sender, RepositoryItemLookUpEdit)
            End If

            If props IsNot Nothing AndAlso (TypeOf e.Value Is Integer) Then
                Dim row As Object = props.GetDataSourceRowByKeyValue(e.Value)
                If row Is Nothing Then
                    e.DisplayText = NotFoundText
                End If
            End If
        End Sub
    End Class
End Namespace