我使用的是DetailsView，但是在更新时，我无法获取OldValues，因为ItemUpdating事件的DetailsViewUpdateEventArgs.OldValues始终为空。 NewValues的值确定。
注意：我没有在应用程序中使用数据源组件（SqlDataSource，ObjectDataSource，EntityDataSource等）。在这种情况下，我应该手动执行一些操作吗？
任何想法都将受到欢迎！
谢谢！
补充信息：
我正在使用ASP.NET 4.0（WebForms）
我认为与以下内容相关的代码段：
<asp:DetailsView ID="customerDetails" runat="server" AutoGenerateRows="False" EmptyDataText="No data..."
meta:resourcekey="customerDetails"
onitemdeleting="customerDetails_ItemDeleting"
oniteminserting="customerDetails_ItemInserting"
onitemupdating="customerDetails_ItemUpdating"
onmodechanging="customerDetails_ModeChanging"
CssClass="customerDetails" DataKeyNames="CustomerID">
<FooterTemplate>
<asp:LinkButton ID="lnkNew" Text="New" ToolTip="New Customer" CommandName="New" meta:resourcekey="lnkNew" runat="server" />
</FooterTemplate>
<EmptyDataTemplate>
<p><asp:Label ID="lblNoDataHasBeenFound" Text="No data has been found." meta:resourcekey="lblNoDataHasBeenFound" runat="server" /></p>
<asp:LinkButton ID="lnkNew" Text="New" ToolTip="New Customer" CommandName="New" meta:resourcekey="lnkNew" runat="server" />
</EmptyDataTemplate>
<Fields>
<%--CustomerID--%>
<asp:TemplateField HeaderStyle-CssClass="detailsHeader" ItemStyle-CssClass="detailsField">
<HeaderTemplate>
<asp:Label ID="ltrCustomerIdLabel" meta:resourcekey="ltrCustomerId" Text="CustomerID:" runat="server" />
</HeaderTemplate>
<ItemTemplate>
<asp:Label ID="lblCustomerId" Text='<%# Eval("CustomerID") %>' runat="server" />
</ItemTemplate>
<EditItemTemplate>
<asp:Label ID="lblCustomerId" Text='<%# Eval("CustomerID") %>' runat="server" />
</EditItemTemplate>
<InsertItemTemplate>
<asp:TextBox ID="txtCustomerId" Text='<%# Bind("CustomerID") %>' MaxLength="5" width="50px" runat="server" />
<cc1:DataAnnotationsValidator ID="CustomerIdValidator" Type="String" runat="server" ControlToValidate="txtCustomerId" PropertyName="CustomerID" Text="*" SourceType="DataLayerPOCO.Customer, DataLayerPOCO" CssError="validationError" Display="None"/>
</InsertItemTemplate>
<HeaderStyle HorizontalAlign="Right" />
<ItemStyle HorizontalAlign="Left" />
</asp:TemplateField>
<%--CompanyName--%>
<asp:TemplateField HeaderStyle-CssClass="detailsHeader" ItemStyle-CssClass="detailsField">
<HeaderTemplate>
<asp:Literal ID="ltrCompanyNameLabel" meta:resourcekey="ltrCompanyName" Text="Company Name:" runat="server" />
</HeaderTemplate>
<ItemTemplate>
<asp:Literal ID="ltrCompanyName" Text='<%# Eval("CompanyName") %>' runat="server"/>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtCompanyName" Text='<%# Bind("CompanyName") %>' MaxLength="40" Width="310px"
runat="server" />
<cc1:DataAnnotationsValidator ID="CompanyNameValidator" Type="String" runat="server" ControlToValidate="txtCompanyName" PropertyName="CompanyName" Text="*" SourceType="DataLayerPOCO.Customer, DataLayerPOCO" CssError="validationError" Display="None"/>
</EditItemTemplate>
<InsertItemTemplate>
<asp:TextBox ID="txtCompanyName" Text='<%# Bind("CompanyName") %>' MaxLength="40" Width="310px"
runat="server" />
<cc1:DataAnnotationsValidator ID="CompanyNameValidator" Type="String" runat="server" ControlToValidate="txtCompanyName" PropertyName="CompanyName" Text="*" SourceType="DataLayerPOCO.Customer, DataLayerPOCO" CssError="validationError" Display="None"/>
</InsertItemTemplate>
<HeaderStyle HorizontalAlign="Right" />
</asp:TemplateField>
...
...
other fields goes here
...
...
<%--Edit/Insert--%>
<asp:TemplateField HeaderStyle-CssClass="detailsHeader" ItemStyle-CssClass="detailsField">
<ItemTemplate>
<asp:ImageButton ID="imgEdit" ImageUrl="~/img/pencil.png" meta:resourcekey="imgEdit" AlternateText="Edit" ToolTip="Edit Customer" CommandName="Edit" runat="server" CausesValidation="false"/>
<asp:ImageButton ID="imgDelete" ImageUrl="~/img/delete.png" meta:resourcekey="imgDelete" AlternateText="Delete" ToolTip="Delete Customer" CommandName="Delete" OnClientClick="return confirmDelete();" runat="server" CausesValidation="false"/>
</ItemTemplate>
<EditItemTemplate>
<asp:ImageButton ID="imgUpdate" ImageUrl="~/img/accept.png" meta:resourcekey="imgUpdate" AlternateText="Update" ToolTip="Update Customer" CommandName="Update" runat="server" />
<asp:ImageButton ID="imgCancel" ImageUrl="~/img/cancel.png" meta:resourcekey="imgCancel" AlternateText="Cancel" ToolTip="Cancel Edit" CommandName="Cancel" runat="server" CausesValidation="false"/>
</EditItemTemplate>
<InsertItemTemplate>
<asp:ImageButton ID="imgSave" ImageUrl="~/img/disk.png" meta:resourcekey="imgSave" AlternateText="Save" ToolTip="Save Customer Data" CommandName="Insert" runat="server" CausesValidation="true"/>
<asp:ImageButton ID="imgCancelInsert" ImageUrl="~/img/cancel.png" meta:resourcekey="imgCancelInsert" AlternateText="Cancel" ToolTip="Cancel Insert" CommandName="Cancel" runat="server" CausesValidation="false"/>
</InsertItemTemplate>
</asp:TemplateField>
<Fields>
</asp:DetailsView>
事件ItemUpdating如下所示：
protected void customerDetails_ItemUpdating(object sender, DetailsViewUpdateEventArgs e)
{
repository = repository ?? new NorthwindRepositoryEF();
string id = e.Keys["CustomerID"] as string;
DataLayerPOCO.Customer customer = repository.GetCustomer(id);
string companyName = (string)e.NewValues["CompanyName"];
string contactName = (string)e.NewValues["ContactName"];
string contactTitle = (string)e.NewValues["ContactTitle"];
string address = (string)e.NewValues["Address"];
string city = (string)e.NewValues["City"];
string region = (string)e.NewValues["Region"];
string postalCode = (string)e.NewValues["PostalCode"];
string country = (string)e.NewValues["Country"];
string phone = (string)e.NewValues["Phone"];
string fax = (string)e.NewValues["Fax"];
// Update Customer with the new data
customer.CompanyName = companyName;
customer.ContactName = contactName;
customer.ContactTitle = contactTitle;
customer.Address = address;
customer.City = city;
customer.Region = region;
customer.PostalCode = postalCode;
customer.Country = country;
customer.Phone = phone;
customer.Fax = fax;
repository.UpdateCustomer(customer);
repository.Save();
//---
customerDetails.ChangeMode(DetailsViewMode.ReadOnly);
BindCustomerDetails();
BindCustomersList();
}
问题是，如果我想处理旧值，则不能：
得出值为0：
int oldValuesCount = e.OldValues.Count;
并且即使我将值更改为一个新值，其结果也为null：
字符串companyNameOld = e.OldValues [“ CompanyName”]作为字符串；
最佳答案
似乎只有在声明性地绑定了数据源时，才会填充旧值。
在这种情况下，您有两种解决方法：
以编程方式将您可能需要的所有旧值保存在ViewState中，并在需要时检索它。这样可以节省前往数据库的行程。
更好的选择是使用您在OnItemUpdating中定义的客户变量，因为它从数据库中查询信息并包含所有旧值。
希望能帮助到你。