Question

I’m using AJAX right now to update my GridView when I search for a string of text in the gridview, or when I select from a dropdownlist what I want to order the Gridview by. This was working previously, but I had really messy code. So I’ve cleaned it up a little bit, added some parameters and such. Unfortunately, now, when the selectedindex of the dropdownlist is changed or when someone tries to search for a field, nothing happens – the page just refreshes. I’m also getting an exception saying “The SELECT item identified by the ORDER BY number 1 contains a variable as part of the expression identifying a column position. Variables are only allowed when ordering by an expression referencing a column name”.

If you need to see any more code then please let me know!

public vieworders()
    {
        this.PreInit += new EventHandler(vieworders_PreInit);
    }

    void vieworders_PreInit(object sender, EventArgs e)
    {
            orderByString = orderByList.SelectedItem.Value;
            fieldString = searchTextBox.Text;
            updateDatabase(fieldString, orderByString);

    }

    protected void updateDatabase(string _searchString, string _orderByString)
    {
        string updateCommand = "SELECT fName,lName,zip,email,cwaSource,price,length FROM SecureOrders WHERE fName LIKE @searchString OR lName LIKE @searchString OR zip LIKE @searchString OR email LIKE @searchString OR cwaSource LIKE @searchString OR length LIKE @searchString OR price LIKE @searchString ORDER BY @orderByString";

        Configuration rootWebConfig = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("/Cabot3");
        ConnectionStringSettings connectionString = rootWebConfig.ConnectionStrings.ConnectionStrings["secureodb"];

        // Create an SqlConnection to the database.
        using (SqlConnection connection = new SqlConnection(connectionString.ToString()))
        using (SqlCommand _fillDatabase = new SqlCommand(updateCommand, connection))
        {

            connection.Open();
            _fillDatabase.Parameters.Add("@searchString", SqlDbType.VarChar, 50).Value = _searchString;
            _fillDatabase.Parameters.Add("@orderByString", SqlDbType.VarChar, 50).Value = _orderByString;
            _fillDatabase.ExecuteNonQuery();

            dataAdapter = new SqlDataAdapter("SELECT * FROM SecureOrders", connection);

            // create the DataSet
            dataSet = new DataSet();
            // fill the DataSet using our DataAdapter               
            dataAdapter.Fill(dataSet, "SecureOrders");

            DataView source = new DataView(dataSet.Tables[0]);
            DefaultGrid.DataSource = source;
            DefaultGrid.DataBind();
            connection.Close();
        }
    }

Form

<form id="form1" runat="server">
<asp:ScriptManager ID = "ScriptManager" runat="server" />
    <div>
        <asp:Label runat="server" id = "orderByLabel" Text = "Order By: " />


        <asp:DropDownList runat="server" ID="orderByList" AutoPostBack="true">
            <asp:ListItem Value="fName" Selected="True">First Name</asp:ListItem>
            <asp:ListItem Value="lName">Last Name</asp:ListItem>
            <asp:ListItem Value="state">State</asp:ListItem>
            <asp:ListItem Value="zip">Zip Code</asp:ListItem>
            <asp:ListItem Value="cwaSource">Source</asp:ListItem>
            <asp:ListItem Value="cwaJoined">Date Joined</asp:ListItem>
        </asp:DropDownList>
    </div>
    <div>
        <asp:Label runat="server" ID="searchLabel" Text="Search For: " />
        <asp:TextBox ID="searchTextBox" runat="server" Columns="30" />
        <asp:Button ID="searchButton" runat="server" Text="Search" />
    </div>
<div>
<asp:UpdatePanel ID = "up" runat="server">



    <ContentTemplate>
    <div style= "overflow:auto; height:50%; width:100%">
    <asp:GridView ID="DefaultGrid" runat = "server" DataKeyNames = "IdentityColumn"
    onselectedindexchanged = "DefaultGrid_SelectedIndexChanged"
    autogenerateselectbutton = "true">
    <SelectedRowStyle BackColor="Azure"
    forecolor="Black"
    font-bold="true" />
    <Columns>
    <asp:TemplateField HeaderText="Processed">
                <ItemTemplate>
                    <asp:CheckBox ID="CheckBoxProcess" AutoPostBack = "true" Checked ='<%#Eval("processed") %>' OnCheckedChanged="CheckBoxProcess_CheckedChanged"  runat="server" Enabled="true" />
                </ItemTemplate>
            </asp:TemplateField>
    </Columns>
    </asp:GridView>
    </div>
    </div>
    <div style= "overflow:auto; height:50%; width:100%" />
    <table border="1">
        <tr>    
        <td>Name: </td>
        <td><%=name %></td>
        </tr>
        <tr>
        <td>Zip: </td>
        <td><%=zip %></td>
        </tr>
        <tr>
        <td>Email: </td>
        <td><%=email %></td>
        </tr>
        <tr>
        <td>Length: </td>
        <td><%=length %></td>
        </tr>
        <tr>
        <td>Price: </td>
        <td><%=price %></td>
        </tr>
        <tr>
        <td>Source: </td>
        <td><%=source %></td>
        </tr>
    </table>
    </div>
    </ContentTemplate>
    </asp:UpdatePanel>



</div>
</form>

Answer 1

I have never used the UpdatePanel since my company uses Telerik, but from the examples I see during my research I remember seeing a trigger component.

From my understanding, if the control is w/i the UpdatePanel itself, then you do not have to specify the trigger, since it is assumed.

For your scenario, the trigger (dropdownlist) is outside of the UpdatePanel. You may need to include this in your aspx:

<asp:UpdatePanel ID = "up" runat="server">
<Triggers>
    <asp:AsyncPostBackTrigger ControlID="orderByList" >
</Triggers>
<ContentTemplate>
    ...