ASP.NET SqlDataSource filter behaviour

Question

I have a GridView object feed trough a SqlDataSource . In the same form I have also a number of textBoxes used to build a filtering expression for the datasource. The 'filtering' is started by pressing a button.

<asp:GridView
    DataSourceID="_sdsTable1"
    OnSorting="_gvTable1_Sorting"
    OnPageIndexChanging="_gvMovimenti_PageIndexChanging"
    runat="server"
    CssClass="list_table"
    ID="_gvTable1"
    CellPadding="0" CellSpacing="0"
    AutoGenerateColumns="false"
    EmptyDataText="No data."
    ShowHeader="true" ShowFooter="true"
    AllowSorting="true"
    AllowPaging="true"
    PageSize="10" 
    OnRowDataBound="_gvMovimenti_RowDataBound" >
    <HeaderStyle CssClass="header" />
    <FooterStyle CssClass="footer" />
    <PagerSettings
        Visible="true"
        Mode="NumericFirstLast"
        PageButtonCount="3"
        Position="Bottom"
        NextPageText="Next page"
        PreviousPageText="Prev page"
        FirstPageText="First page"
        LastPageText="Last page" />
    <RowStyle CssClass="odd" />
    <AlternatingRowStyle CssClass="even" />
    <PagerStyle HorizontalAlign="Center" />
    <Columns>
        <asp:TemplateField Visible="false">
         <HeaderTemplate>&nbsp;</HeaderTemplate>
         <ItemTemplate>
          <%#Eval("id")%>
         </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Date" SortExpression="date">
         <ItemTemplate>
          <%#Eval("date","{0:dd/MM/yyyy HH:mm:ss}")%>
         </ItemTemplate>
         <FooterTemplate>
          TOTALE:
         </FooterTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Price" SortExpression="price">
         <ItemTemplate>
          <asp:Label ID="_lblPrice" runat="server" Text='<%# Bind("price","{0:F2} &euro;") %>'>></asp:Label>
         </ItemTemplate>
         <FooterTemplate>
          <asp:Label ID="_lblTotal" runat="server" Text="0"></asp:Label
         </FooterTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="description" HeaderText="Description" SortExpression="description" />
    </Columns>
</asp:GridView>

<asp:SqlDataSource ID="_sdsTable1" runat="server"
    ConnectionString="<%$ ConnectionStrings:_db %>"
    ProviderName="<%$ ConnectionStrings:_db.ProviderName %>" 
    SelectCommand=" SELECT * FROM view1 WHERE id_user = @id_user;">
    <SelectParameters>
        <asp:SessionParameter Type="Int32" Name="id_user" SessionField="USER_ID" />
    </SelectParameters>
</asp:SqlDataSource>

In codebehind (in the event hanlder associated with the 'button' mentioned above) I build up the filter expression chaining the textbox values, with this code:

    if (!string.IsNullOrWhiteSpace(_txtFilter0.Text.Trim()))
    {
        _sFilter += "(descrizione LIKE '%" + _txtFilter0.Text.Trim() + "%')";
    }

    if (!string.IsNullOrWhiteSpace(_txtFilter1.Text.Trim()))
    {
        if (!string.IsNullOrWhiteSpace(_sFilter))
            _sFilter += " AND";

        _sFilter += "(descrizione LIKE '%" + _txtFilter1.Text.Trim() + "%')";
    }

    _sdsTable1.FilterExpression = _sFilter;

Everything works until I clear the fields that leads to an empty filter. I expected to retrieve all the data. For some reason, in this case, the last recordset is kept and shown apparently without a reason.

I tried also to disable the SQLDataSource caching feature without luck:

    EnableCaching="false"

I tried also to issue a Select command, again without luck:

 _sdsCrediti.Select(DataSourceSelectArguments.Empty);

Where I'm wrong?

Answer 1

Your _sFilter property will be persisted across postbacks, so as you're only updating it when your filter text boxes are not empty it will remain at the last set value when you clear them. Putting a breakpoint in your code at the line _sdsTable1.FilterExpression = _sFilter; should confirm this.

To solve the issue, either clear the _sFilter property before rebuilding it in your event handler, or write an additional check:

if (string.IsNullOrWhiteSpace(_txtFilter1.Text.Trim()) & string.IsNullOrWhiteSpace(_txtFilter0.Text.Trim()) )
{
  _sFilter = null;
}