Question

I have a ListView with an IEnumerable<MyDocument> DataSource pulled from a method.

The code in myDocsList_ItemCommand() definitely runs, because the document is actually deleted. My problem is that the ListView still shows the (now deleted) document until the next page refresh, even though I have code to do myDocsList.Items.Remove(dataItem).

The simplified .ascx is basically:

<asp:ListView id="myDocsList" runat="server" 
        OnItemDataBound="myDocsList_ItemDataBound" 
        OnItemDeleting="myDocsList_ItemDeleting" 
        OnItemCommand="myDocsList_ItemCommand">
    <LayoutTemplate>
        <table>
            <asp:Placeholder id="itemPlaceholder" runat="server" />
        </table>
    </LayoutTemplate>
    <ItemTemplate>
        <tr><td>
                <asp:LinkButton 
                    ID="delete" runat="server"
                    CommandName="Delete" CommandArgument="X"
                    OnClientClick="javascript:return confirm('...');">
                        Delete
                </asp:LinkButton>
        </td></tr>
    </ItemTemplate>
</asp:ListView>

The simplified .ascx.cs is basically:

protected void Page_Load(object sender, EventArgs e)
{
}

protected void Page_PreRender(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        IEnumerable<MyDocument> docs = getDocuments();
        myDocsList.DataSource = docs;
        myDocsList.DataBind();
    }
}

/* so we have the ID of the document we're deleting later on */
protected void myDocsList_ItemDataBound(object sender, 
                                        ListViewItemEventArgs e)
{
    var deleteButton = 
        (LinkButton) ((Control) e.Item).FindControl("delete");
    deleteButton.CommandArgument =
        ((MyDocument) e.Item.DataItem).id.ToString();
}

/* or we get "raised event ItemDeleting which wasn't handled" */
protected void myDocsList_ItemDeleting(Object sender, 
                                        ListViewDeleteEventArgs e)
{
}

/* do something here? */
//protected void myDocsList_ItemDeleted(Object sender, 
//                                      ListViewDeletedEventArgs e)
//{
//}

protected void myDocsList_ItemCommand(object sender, 
                                        ListViewCommandEventArgs e)
{
    if (e.CommandName == "Delete")
    {
        int docId = int.Parse(e.CommandArgument.ToString());
        deleteDocument(docId);
        ListViewDataItem dataItem = (ListViewDataItem) e.Item;
        myDocsList.Items.Remove(dataItem);
    }
}

I’ve been reading up on the ASP page lifecycle and a few related questions, but I’m reasonably inexperienced with ASP and a bit lost.

How do I get my ListView items to disappear on the PostBack instead of on the next page refresh?

Answer 1

You have to rebound data to your ListView in ItemCommand event, you can change your coding style as below:

//Create a new method for databind
void BindData()
{
    IEnumerable<MyDocument> docs = getDocuments();
    myDocsList.DataSource = docs;
    myDocsList.DataBind();
}

//Call databind method in your prerender event
protected void Page_PreRender(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindData();
    }
}

//Again bind data after delete operation
protected void myDocsList_ItemCommand(object sender,
       ListViewCommandEventArgs e)
{
    if (e.CommandName == "Delete")
    {
        int docId = int.Parse(e.CommandArgument.ToString());
        deleteDocument(docId);
        BindData();
    }
}