<%@ Page Language="C#" AutoEventWireup="false"   %>
<%@ Import Namespace="System.Data" %>

<script runat='server'>
    private DataTable dt;
    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);
        Page.Load += new EventHandler(Page_Load);
        Page.PreRender += new EventHandler(Page_PreRender);
        DataGrid1.ItemCommand += new DataGridCommandEventHandler(DataGrid1_ItemCommand);


    }

    void DataGrid1_ItemCommand(object source, DataGridCommandEventArgs e)
    {
        Int32 rowID = (Int32)DataGrid1.DataKeys[e.Item.ItemIndex];
        Int32 rowIndex = 0;
        DataRow rowToBeMoved = dt.NewRow();    //create a copy of the row to be moved
        for (Int16 i = 0; i < dt.Rows.Count; i++)
        {
            if (dt.Rows[i]["ID"].Equals(rowID))
            {
                rowIndex = i;
                rowToBeMoved["ID"] = dt.Rows[i]["ID"];
                rowToBeMoved["PageName"] = dt.Rows[i]["PageName"];
                break;
            }
        }

        switch (e.CommandName)
        {
            case "MoveUp":
                if (rowIndex > 0)
                {
                    //delete the selected row
                    dt.Rows[rowIndex].Delete();
                    dt.AcceptChanges();
                    //add the rowToBeMoved
                    dt.Rows.InsertAt(rowToBeMoved, rowIndex - 1);
                    dt.AcceptChanges();
                    DataGrid1.SelectedIndex = rowIndex - 1;

                }
                break;
            case "MoveDown":
                if (rowIndex < dt.Rows.Count - 1)
                {
                    dt.Rows[rowIndex].Delete();
                    dt.AcceptChanges();
                    dt.Rows.InsertAt(rowToBeMoved, rowIndex + 1);
                    dt.AcceptChanges();
                    DataGrid1.SelectedIndex = rowIndex + 1;
                }
                break;
        }

        Session["FilesOrder"] = dt;
    }


    void Page_Load(object sender, EventArgs e)
    {
        CreateDT();

    }

    void Page_PreRender(object sender, EventArgs e)
    {
        if (dt != null)
        {
            DataGrid1.DataSource = dt;
            DataGrid1.DataBind();
        }
    }

    private DataTable CreateDT()
    {

        if (Session["FilesOrder"] == null)
        {
            dt = new DataTable("FilesOrder");
            DataRow dr;
            dt.Columns.Add(new DataColumn("ID", typeof(Int32)));
            dt.Columns.Add(new DataColumn("PageName", typeof(string)));
            Int16 i = 0;
            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "default.aspx";
            dt.Rows.Add(dr);
            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "default.htm";
            dt.Rows.Add(dr);
            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "default.asp";
            dt.Rows.Add(dr);
            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "index.htm";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "index.aspx";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "index.asp";
            dt.Rows.Add(dr);
            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "main.htm";
            dt.Rows.Add(dr);
            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "main.aspx";
            dt.Rows.Add(dr);
            dr = dt.NewRow();
            dr[0] = i++;
            dr[1] = "main.asp";
            dt.Rows.Add(dr);
            DataColumn[] PrimaryKeyColumns = new DataColumn[1];
            PrimaryKeyColumns[0] = dt.Columns["ID"];
            dt.PrimaryKey = PrimaryKeyColumns;
            Session["FilesOrder"] = dt;
        }
        else
        {
            dt = (DataTable)Session["FilesOrder"];
        }
        return dt;

    }
</script>

<asp:Content ID="Content1" runat="server" ContentPlaceHolderID="MainContent">
    <div style="width: 750px;">
    <h2>
        DataGrid Rows Reordering
    </h2>
    <p>
        Unlike sorting the DataGrid based on an index field, re-ordering the rows, based
        on explicit user requests (to move a row up or down), is not as simple.
    </p>
    <p>
        The approach that one takes is very much dependent on the type of data structure
        one has bound to the datagrid. I can offer here 2 approaches:</p>
    <ol>
        <li>sort based on a rank field. Then upon moving up or down swap the value of that field
            with the previous or next record respectively. </li>
        <li>locate the record that is to be moved using the DataGrid.DataKeys collection while
            processing the DataGrid.ItemCommand event. I make a copy of that DataTableRow then
            delete the original one, acceptChanges on the DataTable, then re-insert it at the
            desired position (whether moving up or down). This approach can pose concurrency
            issues upon saving the table to the database because of the primary keys sequence.
        </li>
    </ol>
 <asp:DataGrid ID="DataGrid1" runat="server" DataKeyField="ID" AutoGenerateColumns="false"  SelectedItemStyle-BackColor="Gold" ItemStyle-BackColor="White" >
        
        <HeaderStyle CssClass="Col1Header"></HeaderStyle>
        <Columns>
            <asp:TemplateColumn>
                <ItemTemplate>
                    <asp:ImageButton runat="server" ToolTip="Click to move this row up" ImageUrl="~/App_Themes/WEBSWAPP/images/up.gif"
                        ID="btnUp" CommandName="MoveUp" />
                    <asp:ImageButton runat="server" ToolTip="Click here to move this row down" ImageUrl="~/App_Themes/WEBSWAPP/images/down.gif"
                        ID="ImageButton1" CommandName="MoveDown" />
                </ItemTemplate>
            </asp:TemplateColumn>
            <asp:BoundColumn DataField="PageName" HeaderText="Page Name" >
            </asp:BoundColumn>
        </Columns>
    </asp:DataGrid>
    </div>
</asp:Content>