c# - Find Control Inside ListView Control

Question

I want to find "Label" control with ID = "Label" inside the "ListView" control. I was trying to do this with the following code:

((Label)this.ChatListView.FindControl("Label")).Text = "active";

But I am getting this exception: Object reference not set to an instance of an object .

What is wrong here ?

This is aspx code:

<asp:ListView ID="ChatListView" runat="server" DataSourceID="EntityDataSourceUserPosts">
    <ItemTemplate>
        <div class="post">
            <div class="postHeader">
                <h2><asp:Label ID="Label1" runat="server" 
                    Text= '<%# Eval("Title")  + " by " + this.GetUserFromPost((Guid?)Eval("AuthorUserID")) %>' ></asp:Label></h2>
                <asp:Label ID="Label" runat="server" Text="" Visible="True"></asp:Label>
                <div class="dateTimePost">
                   <%# Eval("PostDate")%>
                </div>
            </div>
            <div class="postContent">
                <%# Eval("PostComment") %>
            </div>
        </div>
    </ItemTemplate>

</asp:ListView>

Answer 1

Listview is a databound control; so controls inside it will have different ids for different rows. You have to first detect the row, then grab the control. Best to grab such controls is inside an event like OnItemDataBound. There, you can do this to grab your control:

protected void myListView_ItemDataBound(object sender, ListViewItemEventArgs e)
{
    if (e.Item.ItemType == ListViewItemType.DataItem)
    {
        var yourLabel = e.Item.FindControl("Label1") as Label;

        // ...
    }
}

If you want to grab it in Page_Load, you will have to know specific row and retrieve the control as:

var theLabel = this.ChatListView.Items[<row_index>].FindControl("Label1") as Label;