尝试为asp.net中没有数据源控件的列表视图创建datapager时遇到绑定错误

Question

I am trying to create a datapager for my list view on the bottom of the page. When i bind the listview without the datapager i get no error and all of the content gets listed like it should. But when i try to create a datapager i get an error that says: list needs a datasource or need an ICollection as a datasource if AllowPaging is true

Here is my listview:

<asp:ListView ID="lstAllProducts" runat="server">
        <ItemTemplate>
            <a style="color: black" href="ProductInfo.aspx?id=<%# Eval("itemId") %>">
                <div class="wrpInnerItem hvr-fade">
                    <div class="innerItem">
                        <p><%#Eval("gtin")%></p>
                    </div>
                    <div class="innerItem">
                        <p><%#Eval("brandName")%></p>
                    </div>
                    <div class="innerItem">
                        <p><%#Eval("functionalName")%></p>
                    </div>
                    <div class="innerItem">
                        <p><%#Eval("unitDescription")%></p>
                    </div>
                    <div class="innerItem">
                        <p><%#Eval("articleNr")%></p>
                    </div>
                </div>
            </a>
        </ItemTemplate>
    </asp:ListView>

And here is the datapager:

<asp:DataPager ID="DataPager1" runat="server" PagedControlID="lstAllProducts" PageSize="12">
        <Fields>
            <asp:NextPreviousPagerField ButtonType="Link" ShowFirstPageButton="true" ShowLastPageButton="true" />
        </Fields>
    </asp:DataPager>

And here is where i bind the data for the listview in the page load:

if (!IsPostBack)
        {
            lstAllProducts.DataSource = svc.GetAllItemsOverview().OrderByDescending(i => i.id);
            lstAllProducts.DataBind();
        }

I have tried to follow the guide in this link. http://weblogs.asp.net/hajan/paging-listview-using-datapager-without-using-datasource-control

hope some of you have a suggestion on why it wont work.

Answer 1

The problem with your code is that DataPager needs complete data for calculating the page numbers but you are assigning IEnumerable<T> to your ListView which will be resolved while binding the data (You can read about LINQ Deferred Execution ).

To solve the issue simply enumerate the results using ToArray or ToList :-

lstAllProducts.DataSource = svc.GetAllItemsOverview()
                               .OrderByDescending(i => i.id)
                               .ToArray();