sorting on vb.net gridview - asp.net

Question

trying to implement a sort on my gridview as below, its not quite working as I'd expect 1. it doesn't sort by the first column as i'd like, first column descending 2. when i click each of the columns they appear to change order but i can't determine what is actually sorting asc/desc. i really only need the first column which is the id to sort desc.
Imports System.Data.SqlClient
Public Class Query
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
BindGrid()
End If
End Sub
Protected Sub BindGrid()
Dim dt As New DataTable()
Dim strConnString As [String] = System.Configuration.ConfigurationManager.ConnectionStrings("constr").ConnectionString()
Dim strQuery As String = "select id,relates_to,'../../' + location as location from Files;"
Dim cmd As New SqlCommand(strQuery)
Dim con As New SqlConnection(strConnString)
Dim sda As New SqlDataAdapter()
cmd.CommandType = CommandType.Text
cmd.Connection = con
Try
con.Open()
sda.SelectCommand = cmd
sda.Fill(dt)
ViewState("dt") = dt
GridView1.DataSource = dt
GridView1.DataBind()
Catch ex As Exception
Response.Write(ex.Message)
Finally
con.Close()
sda.Dispose()
con.Dispose()
End Try
End Sub
Protected Sub OnRowDataBound(sender As Object, e As GridViewRowEventArgs)
If e.Row.RowType = DataControlRowType.DataRow Then
Dim item As String = e.Row.Cells(0).Text
For Each button As Button In e.Row.Cells(3).Controls.OfType(Of Button)()
If button.CommandName = "Delete" Then
button.Attributes("onclick") = "if(!confirm('Do you want to delete " + item + "?')){ return false; };"
End If
Next
End If
End Sub
Protected Sub OnRowDeleting(sender As Object, e As GridViewDeleteEventArgs)
Try
Using conn As New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ToString())
Dim cmd As New SqlCommand()
cmd.Connection = conn
cmd.CommandText = "DELETE FROM Files WHERE id = #id"
cmd.CommandType = CommandType.Text
Dim strBetID As String = GridView1.Rows(e.RowIndex).Cells(0).Text
cmd.Parameters.Add("#id", SqlDbType.Int).Value = strBetID
conn.Open()
cmd.ExecuteNonQuery()
End Using
BindGrid()
Catch ex As Exception
Response.Write(ex.Message)
End Try
End Sub
Private Sub LinkButtonUsers_Click(sender As Object, e As EventArgs) Handles LinkButtonUsers.Click
Response.Redirect("/Admin/Admin/Users.aspx")
End Sub
Private Sub LinkButtonTips_Click(sender As Object, e As EventArgs) Handles LinkButtonTips.Click
Response.Redirect("/Admin/Admin/Admin.aspx")
End Sub
Private Sub LinkButtonEmail_Click(sender As Object, e As EventArgs) Handles LinkButtonEmail.Click
Response.Redirect("/Admin/Admin/Email.aspx")
End Sub
Private Sub LinkButtonKnowledge_Click(sender As Object, e As EventArgs) Handles LinkButtonKnowledge.Click
Response.Redirect("/Admin/Admin/Knowledge.aspx")
End Sub
Protected Sub LinkButtonQuery_Click(sender As Object, e As EventArgs) Handles LinkButtonQuery.Click
Response.Redirect("/Admin/Admin/Query.aspx")
End Sub
Protected Sub OnPageIndexChanging(sender As Object, e As GridViewPageEventArgs)
GridView1.PageIndex = e.NewPageIndex
Me.BindGrid()
End Sub
Protected Sub GridView1_Sorting(sender As Object, e As GridViewSortEventArgs)
Dim dt As DataTable = ViewState.Item("dt")
Dim dv As DataView = dt.DefaultView
Dim sd As String = ""
If Not dt Is Nothing Or Not dt Is "" Then
If e.SortDirection.ToString.Contains("asc") Then
sd = "asc"
ElseIf e.SortDirection.ToString.Contains("desc") Then
sd = "desc"
Else
sd = "asc"
End If
End If
Try
dv.Sort = e.SortExpression + " " + sd
dt = dv.ToTable
GridView1.DataSource = dt
GridView1.DataBind()
Catch ex As Exception
End Try
End Sub
End Class
aspx is as such:
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" OnRowDeleting="OnRowDeleting"
OnRowDataBound="OnRowDataBound" EnableModelValidation="True" AllowSorting="true"
OnSorting="GridView1_Sorting" AllowPaging="True" OnPageIndexChanging="OnPageIndexChanging">
<Columns>
<asp:BoundField DataField="ID" HeaderText="ID" SortExpression="id" />
<asp:BoundField DataField="relates_to" HeaderText="relates_to" SortExpression="relates_to" />
<asp:TemplateField HeaderText="Preview Image" SortExpression="location">
<ItemTemplate>
<asp:ImageButton ID="ImageButton1" runat="server" ImageUrl='<%# Eval("location")%>'
Width="100px" Height="100px" Style="cursor: pointer" OnClientClick="return LoadDiv(this.src);" />
</ItemTemplate>
</asp:TemplateField>
<asp:CommandField ShowDeleteButton="True" ButtonType="Button" />
</Columns>
</asp:GridView>
am tempted to re-write the lot again using another approach as i have kind of cobbled this together from a couple of sources on the net and presumed it would be okay? probably something minor like the viewstate aspect but can't fathom it out at the moment!?..

Answer 1

Instead of storing the DataTable in the ViewState, you can call BindGrid from the Sorting event to populate the GridView. If you include the data sorting in that method, it will apply in all situations.
The sorting parameters can be stored in the ViewState (or in Session):
Protected Property SortExpression As String
Get
Dim value as Object = ViewState("SortExpression")
Return If(Not IsNothing(value), CStr(value), "id")
End Get
Set(value As String)
ViewState("SortExpression") = value
End Set
End Property
Protected Property IsAscendingSort As Boolean
Get
Dim value as Object = ViewState("IsAscendingSort")
Return If(Not IsNothing(value), CBool(value), False)
End Get
Set(value As Boolean)
ViewState("IsAscendingSort") = value
End Set
End Property
They can be set in the Sorting event handler:
Protected Sub GridView1_Sorting(sender As Object, e As GridViewSortEventArgs)
If e.SortExpression = SortExpression Then
IsAscendingSort = Not IsAscendingSort
Else
SortExpression = e.SortExpression
End If
BindGrid()
End Sub
And used in the BindGrid method:
Protected Sub BindGrid()
...
sda.Fill(dt)
Dim dv As DataView = dt.DefaultView
dv.Sort = SortExpression + " " + If(IsAscendingSort, "ASC", "DESC")
GridView1.DataSource = dv
GridView1.DataBind()
...
End Sub