通过前面几篇，我们已经完成了内容类型，列表定义，列表实例的开发。本篇继续讲解列表中的一个重要环节——事件接收器开发。
我们的场景是：我希望之前做好的订单列表这个内容类型自动地具有某些事件特征，例如当用户在添加一个条目的时候，检查订购日期，如果小于今天的话，就不让添加。（这只是一个假设的场景，现实工作中可以依照业务逻辑而定）
我们应该如何实现这个需求呢？Follow me
1.添加一个事件接收器
下面是默认生成的两个文件
<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="/sharepoint/">
<Receivers ListTemplateId="10000">
<Receiver>
<Name>OrderItemEventReceiverItemAdding</Name>
<Type>ItemAdding</Type>
<Assembly>$SharePoint.Project.AssemblyFullName$</Assembly>
<Class>OrderListSolution.OrderItemEventReceiver.OrderItemEventReceiver</Class>
<SequenceNumber>10000</SequenceNumber>
</Receiver>
</Receivers>
</Elements>
2. 修改有关代码实现业务逻辑
using System;using System.Security.Permissions;using Microsoft.SharePoint;using Microsoft.SharePoint.Security;using Microsoft.SharePoint.Utilities;using Microsoft.SharePoint.Workflow; namespace OrderListSolution.OrderItemEventReceiver{/// <summary>/// List Item Events/// </summary>public class OrderItemEventReceiver : SPItemEventReceiver{/// <summary>/// An item is being added./// </summary>public override void ItemAdding(SPItemEventProperties properties){ SPItemEventDataCollection data = properties.AfterProperties;SPList list = properties.OpenWeb().Lists[properties.ListId];string fieldName= list.Fields.GetField("订购日").InternalName; var date = DateTime.Parse(data[fieldName].ToString());if (date > DateTime.Now){properties.ErrorMessage = "当前添加的日期不合法";properties.Cancel = true;return; } } }}
3.部署和调试，按下F5键
【注意】我们这里故意将订购日设置于大于当前日期。根据事件中的逻辑，我们预期它会报告一个错误，而且取消当前的提交
我们看到了这个错误页面，看起来有些吓人，不是吗？对于一般用户来说，他们可能要被吓坏了
接下来，我们可以定义一个专门的页面来显示错误消息，提高用户体验
然后修改一下代码
using System;using System.Security.Permissions;using Microsoft.SharePoint;using Microsoft.SharePoint.Security;using Microsoft.SharePoint.Utilities;using Microsoft.SharePoint.Workflow;namespace OrderListSolution.OrderItemEventReceiver{/// <summary>/// List Item Events/// </summary>public class OrderItemEventReceiver : SPItemEventReceiver{/// <summary>/// An item is being added./// </summary>public override void ItemAdding(SPItemEventProperties properties){SPItemEventDataCollection data = properties.AfterProperties;SPList list = properties.OpenWeb().Lists[properties.ListId];string fieldName= list.Fields.GetField("订购日").InternalName;var date = DateTime.Parse(data[fieldName].ToString());if (date > DateTime.Now){//properties.ErrorMessage = "当前添加的日期不合法";properties.Status = SPEventReceiverStatus.CancelWithRedirectUrl;properties.RedirectUrl = "/_layouts/OrderListSolution/ErrorPage.aspx";properties.Cancel = true;}}}}
