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DataGrid/GridView Paging and Sorting Using A DataReader - DataGrid Paging and Sorting using a DataReader and Structure Class/ArrayList

DMarko1

DataGrid Paging and Sorting using a DataReader and Structure Class/ArrayList

<%@ Page Language="VB" Debug="False" Strict="True"
    Explicit="True" Buffer="True" Trace="False" %>
<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

<html>
<head></head>
<body bgcolor="#FFFFFF" topmargin="0" marginheight="0">

<script language="VB" runat="server">
    'Set up the variables for our ArrayLists
    Dim dgCache, bkResults As ArrayList

    Sub Page_Load (Source As Object, E As EventArgs)
        If Not Page.IsPostBack Then
            'Reset DataGrid Page to the top
            MyDataGrid.CurrentPageIndex = 0
            'Check if ViewSate is already populated
            If IsNothing(ViewState("SortOrder")) then
                'Assign default column sort order
                GetDataReader ("SupplierID asc")
            Else
                'Else retrieve sort order from ViewState
                GetDataReader (ViewState("SortOrder").ToString())
            End If
        End If
    End Sub


    Public Structure DBInfo 'Lightweight Class to hold our data results

        Private _SupplierID As Object
        Private _CompanyName As String
        Private _ContactName As String
        Private _Country As String

        'Constructor
        Public Sub New (ByVal SupplierID As Object, ByVal CompanyName As String, _
        ByVal ContactName As String, ByVal Country As String)

            _SupplierID = SupplierID
            _CompanyName = CompanyName
            _ContactName = ContactName
            _Country = Country

        End Sub


        'All relevant public properties based on database columns
        Public Property SupplierID() As Object
            Get
                Return _SupplierID
            End Get
            Set (ByVal Value As Object)
                _SupplierID = Value
            End Set
        End Property

        Public Property CompanyName() As String
            Get
                Return _CompanyName
            End Get
            Set (ByVal Value As String)
                _CompanyName = Value
            End Set
        End Property

        Public Property ContactName() As String
            Get
                Return _ContactName
            End Get
            Set (ByVal Value As String)
                _ContactName = Value
            End Set
        End Property

        Public Property Country() As String
            Get
                Return _Country
            End Get
            Set (ByVal Value As String)
                _Country = Value
            End Set
        End Property

    End Structure 'DBinfo Structure


    Function SortOrder (Field As String) As String

        If Field = ViewState("SortOrder").ToString() Then
            SortOrder = Replace (Field,"asc","desc")
        Else
            SortOrder = Replace (Field,"desc","asc")
        End If

    End Function


    Sub GetDataReader(ColumnOrder As String)

        'Assign ColumnOrder to ViewState
        ViewState("SortOrder") = ColumnOrder

        'Set up Cache Object and determine if it exists
        dgCache = CType(Cache.Get("dgCache" & ColumnOrder), ArrayList)

        If (dgCache Is Nothing) Then

            Dim sqlStr As String = "SELECT SupplierID, CompanyName, "_
                  & "ContactName, Country FROM Suppliers Order by " & ColumnOrder
            Dim strConn As String = "server=(local);uid=sa;pwd=;database=Northwind;"
            Dim MyConnection As New SQLConnection (strConn)

            MyConnection.Open()

            Dim MyCommand As New SQLCommand(sqlStr, MyConnection)
            Dim objDataReader As SQLDataReader = MyCommand.ExecuteReader (CommandBehavior.CloseConnection)
            'Create instances of the class,
            Dim bkResults as New ArrayList()

            'Loop through DataReader
            While objDataReader.Read()

                With bkResults

                    'and then add the instances to the ArrayList
                    .Add (New DBInfo (objDataReader.GetInt32(0), _
                             objDataReader.GetString(1), _
                             objDataReader.GetString(2), _
                             objDataReader.GetString(3)))
                End With
            End While

            'Insert ArrayList into Cache Object with unique identifier
            Cache.Insert ("dgCache" & ColumnOrder, bkResults)
            'Close DataReader Connection
            objDataReader.Close()
            'Bind DataGrid from ArrayList
            MyDataGrid.DataSource = bkResults
        Else
            'Bind DataGrid from Cached ArrayList
            MyDataGrid.DataSource = dgCache
        End If

        MyDataGrid.DataBind()

        'Clear ArrayList
        bkResults = Nothing
    End Sub

    Sub MyDataGrid_Page(sender As Object, e As DataGridPageChangedEventArgs)
        MyDataGrid.CurrentPageIndex = e.NewPageIndex
        GetDataReader (ViewState("SortOrder").ToString())
    End Sub

    Sub MyDataGrid_Sort(sender As Object, e As DataGridSortCommandEventArgs)
        MyDataGrid.CurrentPageIndex = 0
        GetDataReader(SortOrder(e.SortExpression.ToString()))
    End Sub
  
</script>
<br><br>
<b>Dynamic DataGrid Paging and Sorting Using A DataReader Bound ArrayList</b>
<br>
<form runat="server">


<%= "Page: " & MyDataGrid.CurrentPageIndex+1 & " of " & (MyDataGrid.PageCount) %>
<br><br>
  
<ASP:DataGrid id="MyDataGrid" runat="server"

    AutoGenerateColumns="False"
    AllowPaging="True"
    AllowCustomPaging="False"
    AllowSorting="True"
    PageSize="10"
    PagerStyle-Mode="NumericPages"
    PagerStyle-HorizontalAlign="Right"
    PagerStyle-NextPageText="Next"
    PagerStyle-PrevPageText="Prev"
    BorderColor="black"
    BorderWidth="1"
    GridLines="Both"
    CellPadding="3"
    CellSpacing="0"
    Font-Name="Verdana"
    Font-Size="8pt"
    HeaderStyle-BackColor="#aaaadd"
    AlternatingItemStyle-BackColor="#eeeeee"
    Width="700px"
    OnPageIndexChanged="MyDataGrid_Page"
    OnSortCommand="MyDataGrid_Sort" >
    <Columns>
        <asp:BoundColumn DataField="SupplierID" SortExpression="SupplierID asc" HeaderText="SupplierID"/>
        <asp:BoundColumn DataField="CompanyName" SortExpression="CompanyName asc"
        HeaderText="CompanyName"/>
        <asp:BoundColumn DataField="ContactName" HeaderText="ContactName"
        SortExpression="ContactName asc"/>
        <asp:BoundColumn DataField="Country" HeaderText="Country"
        SortExpression="Country asc"/>
    </Columns>
</asp:DataGrid>
</form>
</body>
</html>

Dimitrios, or Jimmy as his friends call him, is a .NET developer/architect who specializes in Microsoft Technologies for creating high-performance and scalable data-driven enterprise Web and desktop applications. Till now Jimmy has authored nearly two dozen .NET articles, published on Dot Net Junkies, 4 Guys From Rolla, Sitepoint, MSDN Academic Alliance, Developers.NET, The Official Microsoft ASP.NET Site, and here on Developer Fusion, covering various unique and advanced techniques on .NET.

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