FindControl not working in Listview Null exception

Question

protected void PassSessionVariable_Click(object sender, EventArgs e)
{
    String strLocationID = livTour.FindControl("lblLocationID").ToString();
}

For some reason, the FindControl is getting a null exception. Any particular reasons?

Here is the code for my Listview. The find control is not finding the LocationID label.

<%--Create datasource for ListView for Tour Locations.--%>
<asp:SqlDataSource runat="server" ID="sdsListViewTour"
    ConnectionString="<%$ConnectionStrings:2020LJCDT %>"
    OldValuesParameterFormatString="original_{0}"
    SelectCommand="SELECT LocationID, Location, Image
                     FROM Location
                    Order BY City;">
</asp:SqlDataSource>

<%--Listview--%>
<asp:ListView runat="server" ID="livTour"
    DataKeyNames="Location" 
    DataSourceID="sdsListViewTour">

    <ItemTemplate>

        <div class="container p-1 bg-light">

            <asp:LinkButton runat="server" ID="PassSessionVariable" OnClick="PassSessionVariable_Click">
                <div class="row border-top border-bottom border-secondary" style="padding-top: 5px; padding-bottom: 5px; padding-left: 20px;">

                    <asp:Label runat="server" ID="lblLocationID" Text='<%# Eval("LocationID") %>' />

                    <div class="col text-center" style="margin: auto; color: #2699FB;">
                        <asp:Label runat="server" CssClass="font-weight-bold" Text='<%# Eval("Location") %>' />
                    </div>

                    <div class="col text-center">
                        <asp:Image runat="server" CssClass="rounded" ImageUrl='<%# "~/Image/Location/" + Eval("Image") %>' />
                    </div>

                </div>
            </asp:LinkButton>

        </div>

    </ItemTemplate>
</asp:ListView>

So what i think is the problem is your control is not being found which returns a value of null so when you call ToString on a null you get a null value exception. You need to refactor your code to check for null first and then you should be returned your control. — jgetner, Apr 08 '20 at 01:58
https://stackoverflow.com/questions/29488363/findcontrol-returning-null this might help you understand how to find it better than me trying to explain it in a comment. — jgetner, Apr 08 '20 at 02:20
@jgetner I'm trying to find the Textbox control that has an ID binded to it in a listview. Then I'm trying to save that ID to a session variable. The find control is not working for some odd reason. — Isiah Jones, Apr 08 '20 at 02:46
So you don't have `txtLocationID` in your ListView, should not be `lblLocationID`? — Selim Yildiz, Apr 08 '20 at 11:42
@SelimYıldız I have been messing around with things. I have tried it with txtLocationID and then also changed it to a lblLocationID. That was a typo I didn't change when copied in. — Isiah Jones, Apr 08 '20 at 11:44

Selim Yildiz · Accepted Answer · 2020-04-08T12:07:06.650

0

You can find location label via BindingContainer of sender as follow:

protected void PassSessionVariable_Click(object sender, EventArgs e)
{
    var locationLabel = (((Control)sender).BindingContainer.FindControl("lblLocationID") as Label);

    String strLocationID = locationLabel.Text;
}

In this case BindingContainer indicates the row of ListItem that you click. So that you can find location label in this row.

edited Apr 08 '20 at 12:07

answered Apr 08 '20 at 11:50

Selim Yildiz

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What exactly does the Binding Container do is this scenario? – Isiah Jones Apr 08 '20 at 12:00
1

In this case BindingContainer indicates list item of row that you click. So that you can find location label via this row. – Selim Yildiz Apr 08 '20 at 12:05

FindControl not working in Listview Null exception

1 Answers1