我是一般编码的新手，有一个任务，我需要使用Visual studio使用ASP.net创建一个时事通讯网站;c#(对不起，如果我把一些术语弄错了，我是新手)
我有上述错误，不太明白是什么问题。
下面是编辑新闻页面的代码。我有2 db的内部连接，你可以看到从选择命令。我想有一个下拉列表，所以作者可以选择一项运动，因为目前在数据库中，它被列为数字，这是没有用的，如果他们不知道数字代表什么。我能够得到一个下拉列表工作，但是，当我添加"SelectedValue"，以便当作者选择一个运动，它会更新数据库，虽然，这是当我得到了错误。我在插入页中有相同的代码字符串，它可以工作，所以任何帮助都会非常感激:)
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="editnews.aspx.cs" Inherits="admin_editnews" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<link href="../css/bootstrap.css" rel='stylesheet' type='text/css' />
<link href="../css/style.css" rel='stylesheet' type='text/css' />
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:SqlDataSource ID="newseditrows" runat="server"
ConnectionString="<%$ ConnectionStrings:newsconnection %>"
SelectCommand="SELECT News.headline, News.Image, News.paragraph, Sports.sport, News.Sport, News.date, News.lead, News.authorID, Sports.id
FROM News
INNER JOIN Sports ON News.Sport = Sports.id
ORDER BY date DESC"
UpdateCommand="UPDATE [News] SET [headline]=@headline, [Image]=@Image, [paragraph]=@paragraph, [Sport]=@sport, [date]=@date, [lead]=@lead, [authorid]=@authorid WHERE [id]=@id">
<UpdateParameters>
<asp:Parameter Name="headline" Type="String" />
<asp:Parameter Name="Image" Type="String" />
<asp:Parameter Name="paragraph" Type="String" />
<asp:Parameter Name="Sport" Type="Int32" />
<asp:Parameter Name="date" Type="String" />
<asp:Parameter Name="lead" Type="String" />
<asp:Parameter Name="authorid" Type="Int32" />
<asp:Parameter Name="ID" Type="Int32" />
</UpdateParameters>
</asp:SqlDataSource>
<asp:SqlDataSource ID="sportlist" runat="server"
ConnectionString='<%$ ConnectionStrings:newsconnection %>'
SelectCommand="SELECT [id], [sport] FROM [Sports]">
</asp:SqlDataSource>
<asp:ListView ID="displayedit" runat="server"
DataSourceID="newseditrows"
DataKeyNames="id">
<AlternatingItemTemplate>
<span style="">id:
<asp:Label Text='<%# Eval("id") %>' runat="server" ID="idLabel" /><br />
headline:
<asp:Label Text='<%# Eval("headline") %>' runat="server" ID="headlineLabel" /><br />
Image:
<asp:Label Text='<%# Eval("Image") %>' runat="server" ID="ImageLabel" /><br />
paragraph:
<asp:Label Text='<%# Eval("paragraph") %>' runat="server" ID="paragraphLabel" /><br />
Sport:
<asp:Label Text='<%# Eval("sport") %>' runat="server" ID="SportLabel" /><br />
date:
<asp:Label Text='<%# Eval("date") %>' runat="server" ID="dateLabel" /><br />
lead:
<asp:Label Text='<%# Eval("lead") %>' runat="server" ID="leadLabel" /><br />
authorID:
<asp:Label Text='<%# Eval("authorID") %>' runat="server" ID="authorIDLabel" /><br />
<asp:Button ID="EditButton" runat="server" CommandName="Edit" Text="Edit" />
<br />
<br />
</span>
</AlternatingItemTemplate>
<EditItemTemplate>
<span style=""><%--id:
<asp:Label Text='<%# Eval("id") %>' runat="server" ID="idLabel1" /><br />--%>
Headline:
<asp:TextBox Text='<%# Bind("headline") %>' runat="server" ID="headlineTextBox" /><br />
Image:
<asp:TextBox Text='<%# Bind("Image") %>' runat="server" ID="ImageTextBox" /><br />
Paragraph:<br />
<asp:TextBox Text='<%# Bind("paragraph") %>' runat="server" ID="paragraphTextBox"
TextMode="MultiLine" Columns="50" Rows="8"/><br />
<br />Sport:
<%--<asp:TextBox ID="SportTextBox" runat="server" Text='<%# Bind("Sport") %>' />--%>
<asp:DropDownList ID="Sport" runat="server"
DataSourceID="sportlist"
DataTextField="sport"
DataValueField="id"
SelectedValue='<%# Bind("Sport") %>' >
</asp:DropDownList>
<br />
<%--date:
<asp:TextBox Text='<%# Bind("date") %>' runat="server" ID="dateTextBox" /><br />--%>
Lead:
<asp:TextBox Text='<%# Bind("lead") %>' runat="server" ID="leadTextBox" /><br />
<%--authorID:
<asp:TextBox Text='<%# Bind("authorID") %>' runat="server" ID="authorIDTextBox" /><br />--%>
<asp:Button runat="server" CommandName="Update" Text="Update" ID="UpdateButton" /><asp:Button runat="server" CommandName="Cancel" Text="Cancel" ID="CancelButton" /><br />
<br />
</span>
</EditItemTemplate>
<EmptyDataTemplate>
<span>No data was returned.</span>
</EmptyDataTemplate>
<InsertItemTemplate>
<span style="">headline:
<asp:TextBox Text='<%# Bind("headline") %>' runat="server" ID="headlineTextBox" /><br />
Image:
<asp:TextBox Text='<%# Bind("Image") %>' runat="server" ID="ImageTextBox" /><br />
paragraph:
<asp:TextBox Text='<%# Bind("paragraph") %>' runat="server" ID="paragraphTextBox" /><br />
Sport:
<asp:TextBox Text='<%# Bind("sport") %>' runat="server" ID="SportTextBox" /><br />
date:
<asp:TextBox Text='<%# Bind("date") %>' runat="server" ID="dateTextBox" /><br />
lead:
<asp:TextBox Text='<%# Bind("lead") %>' runat="server" ID="leadTextBox" /><br />
authorID:
<asp:TextBox Text='<%# Bind("authorID") %>' runat="server" ID="authorIDTextBox" /><br />
<asp:Button runat="server" CommandName="Insert" Text="Insert" ID="InsertButton" /><asp:Button runat="server" CommandName="Cancel" Text="Clear" ID="CancelButton" /><br />
<br />
</span>
</InsertItemTemplate>
<ItemTemplate>
<span style="">id:
<asp:Label Text='<%# Eval("id") %>' runat="server" ID="idLabel" /><br />
headline:
<asp:Label Text='<%# Eval("headline") %>' runat="server" ID="headlineLabel" /><br />
Image:
<asp:Label Text='<%# Eval("Image") %>' runat="server" ID="ImageLabel" /><br />
paragraph:
<asp:Label Text='<%# Eval("paragraph") %>' runat="server" ID="paragraphLabel" /><br />
Sport:
<asp:Label Text='<%# Eval("sport") %>' runat="server" ID="SportLabel" /><br />
date:
<asp:Label Text='<%# Eval("date") %>' runat="server" ID="dateLabel" /><br />
lead:
<asp:Label Text='<%# Eval("lead") %>' runat="server" ID="leadLabel" /><br />
authorID:
<asp:Label Text='<%# Eval("authorID") %>' runat="server" ID="authorIDLabel" /><br />
<asp:Button ID="EditButton" runat="server" CommandName="Edit" Text="Edit" />
<br />
<br />
</span>
</ItemTemplate>
<LayoutTemplate>
<div runat="server" id="itemPlaceholderContainer" style=""><span runat="server" id="itemPlaceholder" /></div>
<div style="">
<asp:DataPager runat="server" ID="DataPager1">
<Fields>
<asp:NextPreviousPagerField ButtonType="Button" ShowFirstPageButton="True" ShowNextPageButton="False" ShowPreviousPageButton="False"></asp:NextPreviousPagerField>
<asp:NumericPagerField></asp:NumericPagerField>
<asp:NextPreviousPagerField ButtonType="Button" ShowLastPageButton="True" ShowNextPageButton="False" ShowPreviousPageButton="False"></asp:NextPreviousPagerField>
</Fields>
</asp:DataPager>
</div>
</LayoutTemplate>
<SelectedItemTemplate>
<span style="">id:
<asp:Label Text='<%# Eval("id") %>' runat="server" ID="idLabel" /><br />
headline:
<asp:Label Text='<%# Eval("headline") %>' runat="server" ID="headlineLabel" /><br />
Image:
<asp:Label Text='<%# Eval("Image") %>' runat="server" ID="ImageLabel" /><br />
paragraph:
<asp:Label Text='<%# Eval("paragraph") %>' runat="server" ID="paragraphLabel" /><br />
Sport:
<asp:Label Text='<%# Eval("sport") %>' runat="server" ID="SportLabel" /><br />
date:
<asp:Label Text='<%# Eval("date") %>' runat="server" ID="dateLabel" /><br />
lead:
<asp:Label Text='<%# Eval("lead") %>' runat="server" ID="leadLabel" /><br />
authorID:
<asp:Label Text='<%# Eval("authorID") %>' runat="server" ID="authorIDLabel" /><br />
<asp:Button ID="EditButton" runat="server" CommandName="Edit" Text="Edit" />
<br />
<br />
</span>
</SelectedItemTemplate>
</asp:ListView>
</div>
</form>
</body>
</html>
ListControl。SelectedValue: 获取列表控件中选定项的值，或选择列表控件中包含指定值的项。(继承自ListControl。)MSDN参考。
在这里，您试图选择值字段中不存在的值。
SelectedValue='<%# Bind("id") %>'应该可以工作。
<asp:DropDownList ID="Sport" runat="server"
DataSourceID="sportlist"
DataTextField="sport"
DataValueField="id"
SelectedValue='<%# Bind("id") %>' >