How to reload GridView based on DropDownList selection dynamically

Question

I'm trying to load/reload a GridView based on the OnSelectedIndexChanged event of a DropDownList. The ddl has AutoPostBack set to true, but still the Grid won't load, unless I encapsulate it within an UpdatePanel. But once I do that, my FileUpload control stops working... What would be the best solution for this problem?

**Edit ** Relevant code:

aspx file

    <asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
        <asp:UpdatePanel ID="upProva" runat="server">
                <ContentTemplate>
                <%--user control for data selection--%>
                <asp:DropDownList ID="ddlAula" runat="server" DataTextField="nmAula" DataValueField="idAula"
                    CssClass="medio" Enabled="false" AutoPostBack="true" OnSelectedIndexChanged="ddlAula_OnSelectedIndexChanged">
                </asp:DropDownList>
            </ContentTemplate>
        </asp:UpdatePanel>
        <asp:GridView ID="gvQuestoes" runat="server" AutoGenerateColumns="False" CssClass="gv"
            AllowSorting="false" DataKeyNames="idQuestao" OnRowCommand="gvQuestao_RowCommand">
            <Columns>
                <%--(...)--%>
            </Columns>
        </asp:GridView>
<asp:Button ID="btnSalvar" runat="server" ToolTip="Salvar" CssClass="botao40 salv40"
                    OnClick="btnSalvar_Click" ValidationGroup="trabalho" />
        <asp:FileUpload ID="fuAnexo" runat="server" CssClass="fileOriginal" />
    </asp:Content>

codebehind

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        btnArquivo.OnClientClick = "document.getElementById('" + fuAnexo.ClientID + "').click(); return false;";
        txtAnexo.Attributes.Add("onclick", "document.getElementById('" + fuAnexo.ClientID + "').click(); return false;");
        fuAnexo.Attributes.Add("onchange", "document.getElementById('" + txtAnexo.ClientID + "').value = this.value;");

    }
}

protected void ddlAula_OnSelectedIndexChanged(object sender, EventArgs e)
{
    gvQuestoes.DataSource = Questao.CarregarPorAula(Int32.Parse(ddlAula.SelectedValue));
    gvQuestoes.DataBind();
}

The DataSource/Databinding is correct (I know because I've added a button to the page, and used the same binding code on the Button _Click event and it works).

Hi add a code please. So it may be possible to show you an example. — hackp0int
– hackp0int, Commented Aug 15, 2014 at 18:06

Rahul · Accepted Answer · 2014-08-15 18:11:58Z

1

You need to rebind the gridview in OnSelectedIndexChanged event. Something like

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
  //Do your processing logic

  gridview1.DataSource = new_modified_datasource;
  gridview1.DataBind();  
}

answered Aug 15, 2014 at 18:11

Rahul

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1 Comment

Marc.2377 Over a year ago

My code already includes that, but unfortunately it won't work unless I encapsulate the GridView inside the UpdatePanel. Have a look at the code I just posted. Thanks

Marc.2377 · Accepted Answer · 2014-08-15 20:17:29Z

I found a fairly simple (though not ideal in all cases) with PostBackTrigger:

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
        <asp:UpdatePanel ID="upProva" runat="server">
                <ContentTemplate>
                <%--user control for data selection--%>
                <asp:DropDownList ID="ddlAula" runat="server" DataTextField="nmAula" DataValueField="idAula"
                    CssClass="medio" Enabled="false" AutoPostBack="true" OnSelectedIndexChanged="ddlAula_OnSelectedIndexChanged">
                </asp:DropDownList>

        <asp:GridView ID="gvQuestoes" runat="server" AutoGenerateColumns="False" CssClass="gv"
            AllowSorting="false" DataKeyNames="idQuestao" OnRowCommand="gvQuestao_RowCommand">
            <Columns>
                <%--(...)--%>
            </Columns>
        </asp:GridView>
        <asp:FileUpload ID="fuAnexo" runat="server" CssClass="fileOriginal" />
   </ContentTemplate>
    <Triggers>
    <asp:PostBackTrigger ControlID="btnSalvar" />    
    </Triggers>
        </asp:UpdatePanel>
    </asp:Content>

Reg Edit · Accepted Answer · 2014-08-15 20:47:09Z

0

Nowhere in your code do you show how you populate ddlAula. So here is my answer: the Page_Load you've shown is abbreviated, and actually you are populating ddlAula there. Furthermore, you are doing it each time, rather than checking IsPostBack. Therefore by the time your eventhandler for ddlAula is hit, the list has been reset and the value you selected is no longer selected.

If my answer is correct, you need to add the check in Page_Load:

if (!IsPostBack)
{
    //populate ddlAula
}

answered Aug 15, 2014 at 20:47

Reg Edit

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1 Comment

Marc.2377 Over a year ago

No, it's populated somewhere else and I didn't include it because it wasn't necessary. My problem was specifically about the FileUploader control not working with asynchronous postback (when inside the UpdatePanel. Thanks anyway.

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