Imports System.Collections
Imports System.Data
Imports System.Web.UI.WebControls

Namespace AlwaysShowHeaderFooter

  Public Delegate Function MustAddARowHandler(ByVal data As IEnumerable) As IEnumerable


  Public Class GridViewAlwaysShow
    Inherits GridView

    'Flag used to identify if the datasource is empty.
    Private _isEmpty As Boolean = False

    Protected Overrides Sub OnDataBound(ByVal e As EventArgs)

      'if in DesignMode, don't do anything special. Just call base and return.
      If DesignMode Then
        MyBase.OnDataBound(e)
        Return
      End If

      'hide the dummy row.
      If _isEmpty Then
        Rows(0).Visible = False
      End If
      MyBase.OnDataBound(e)
    End Sub

    Protected Overrides Sub PerformDataBinding(ByVal data As IEnumerable)

      'If in DesignMode, don't do anything special. Just call base and return.
      If DesignMode Then
        MyBase.PerformDataBinding(data)
        Return
      End If

      'Count the data items.(I wish I knew a better way to do this.)
      Dim objectItemCount As Integer = 0
      For Each o As Object In data
        objectItemCount += 1
      Next

      'If there is a count, don't do anything special. Just call base and return.
      If objectItemCount > 0 Then
        MyBase.PerformDataBinding(data)
        Return
      End If

      'Set these values so the GridView knows what's up.
      SelectArguments.TotalRowCount += 1
      _isEmpty = True

      'If it's a DataView, it will work without having to handle the MustAddARow event.
      If data.[GetType]() Is GetType(DataView) Then
        'Add a row and use that new view.
        Dim dv As DataView = DirectCast(data, DataView)
        dv.Table.Rows.InsertAt(dv.Table.NewRow(), 0)
        MyBase.PerformDataBinding(dv.Table.DefaultView)
        Return
      Else
        'If you are using some custom object, you need to handle this event.
        MyBase.PerformDataBinding(OnMustAddARow(data))
        Return
      End If
    End Sub


    Protected Function OnMustAddARow(ByVal data As IEnumerable) As IEnumerable
      If MustAddARow Is Nothing Then
        Throw New NullReferenceException("The datasource has no rows. You must handle the ""MustAddARow"" Event.")
      End If
      Return MustAddARow(data)
    End Function

    Public Event MustAddARow As MustAddARowHandler

  End Class

End Namespace