转发器内部的ASP：NET Binding下拉列表

Question

我想要做的是转发器内部的绑定和下拉列表，但我没有成功。 我在标记的行中遇到以下错误：System.NullReferenceException。 任何帮助都会得到满足。

后端：

    protected void shoeRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        FixbayDBDataContext db = new FixbayDBDataContext();
        var colors = from c in db.ColorTbls select new { ColorID = c.ColorID, ColorName = c.ColorName, };

        DropDownList ddl = (DropDownList)e.Item.FindControl("colorList1");
        ddl.DataSource = colors; //ERROR LINE
        ddl.DataTextField = "ColorName";
        ddl.DataValueField = "ColorName";
    }

前端：

<ajaxToolkit:TabPanel ID="TabPanel5" runat="server">
                <HeaderTemplate>Show Shoes</HeaderTemplate>
                <ContentTemplate runat="server">                                                               
                    <asp:Repeater ID="shoeRepeater" OnItemCreated="shoeRepeater_ItemDataBound" runat="server">
                        <HeaderTemplate></HeaderTemplate>
                        <ItemTemplate>
                            <table border="1" style="border-color:#ff9900; width:400px; font-weight:bold; font-family:'Oswald', Arial, sans-serif;">
                                <tr>
                                    <td rowspan="6" style="width:150px; height:150px;">
                                        <image src="shoeImages/<%#DataBinder.Eval(Container.DataItem,"ImagePath") %>"></image>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        <%#DataBinder.Eval(Container.DataItem,"BrandName") %> <%#DataBinder.Eval(Container.DataItem,"ModelName") %> 
                                    </td>

                                </tr>
                                <tr>
                                    <td>
                                        Price: $<%#DataBinder.Eval(Container.DataItem,"Price") %>
                                    </td>

                                </tr>
                                <tr>
                                    <td>
                                        Size: <%#DataBinder.Eval(Container.DataItem,"Size") %>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        <asp:DropDownList ID="colorList1" onchange="get(this)" runat="server">
                                        </asp:DropDownList>
                                        Color: <%#DataBinder.Eval(Container.DataItem,"PrimaryColor") %> - <%#DataBinder.Eval(Container.DataItem,"SecondaryColor") %>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        Quantity: <%#DataBinder.Eval(Container.DataItem,"Quantity") %>
                                    </td>

                                </tr>
                            </table>
                        </ItemTemplate>
                        <FooterTemplate></FooterTemplate>
                    </asp:Repeater>
                </ContentTemplate>
            </ajaxToolkit:TabPanel>

Answer 1

您订阅了错误的活动：

OnItemCreated="shoeRepeater_ItemDataBound"

这应该是

OnItemDataBound="shoeRepeater_ItemDataBound"

Answer 2

这是解决方案

    protected void shoeRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        FixbayDBDataContext db = new FixbayDBDataContext();
        var colors = from c in db.ColorTbls select new { ColorID = c.ColorID, ColorName = c.ColorName, };

        if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
        {
            DropDownList ddl = (DropDownList)e.Item.FindControl("colorList1");
            ddl.DataSource = colors;//Or any other datasource.
            ddl.DataTextField = "ColorName";
            ddl.DataValueField = "ColorName";
            ddl.DataBind();
        }
    }