代码段：从客户端上的外部列表中获取项数据
上次修改时间： 2010年4月19日
适用范围： SharePoint Server 2010
本文内容
说明
必备组件
使用该示例
说明
以下代码段演示如何从使用 SharePoint 客户端对象模型的客户端计算机检索外部列表中的列表项数据。
.gif "重要注释") 重要说明 |
|---|
如果您尝试从外部列表中使用 ListItem 数据的"默认"ClientContext.Load，则会收到以下错误："给定关键字不在字典中"。您需要在 CamlQuery 中以及 ClientContext.Load 方法中明确指定所需的字段。 |
必备组件
服务器上安装了 Microsoft SharePoint Server 2010 或 Microsoft SharePoint Foundation 2010。
服务器上至少有一个外部列表。
客户端计算机上安装了 Microsoft Office Professional Plus 2010 和 Microsoft .NET Framework 3.5。
Microsoft Visual Studio。
使用该示例
在客户端计算机上启动 Visual Studio，并创建 C# 控制台应用程序项目。在创建项目时，选择".NET Framework 3.5"。
从"视图"菜单中，单击"属性页"以显示项目属性。
在"生成"选项卡中，为"目标平台"选择"任何 CPU"。
关闭项目属性窗口。
在"解决方案资源管理器"的"引用"下，移除除 System 和 System.Core 之外的所有项目引用。
将以下引用添加到项目中：
Microsoft.SharePoint.Client
Microsoft.SharePoint.Client.Runtime
System.Data.Linq
System.XML
用此过程末尾列出的代码替换 Program.cs 中自动生成的代码。
将 <TargetSiteUrl> 和 <TargetListName> 的值替换为有效值。
保存该项目。
编译并运行该项目。
using System;
using Microsoft.SharePoint.Client;
using System.Linq.Expressions;
using System.Collections.Generic;
using System.Xml;
using System.IO;
using System.Text;
using System.Globalization;
namespace Microsoft.SDK.Sharepoint.Samples
{
/// <summary>
/// This example shows how to retrieve list item data
/// from an external list.
///
/// You'll need to explicitly specify the field data in both
/// the CAML query and also ClientContext.Load.
/// </summary>
class Program
{
// Note: Replace these with your actual Site URL and List name.
private static string TargetSiteUrl = "<TargetSiteUrl>";
private static string TargetListName = "<TargetListName>";
/// <summary>
/// Example to show using CSOM to retrieve external List data.
/// </summary>
static void Main(string[] args)
{
ClientContext clientContext = new ClientContext(TargetSiteUrl);
List externalList = clientContext.Web.Lists.GetByTitle(
TargetListName);
// To properly construct the CamlQuery and
// ClientContext.LoadQuery,
// we need some View data of the Virtual List.
// In particular, the View will give us the CamlQuery
// Method and Fields.
clientContext.Load(
externalList.Views,
viewCollection => viewCollection.Include(
view => view.ViewFields,
view => view.HtmlSchemaXml));
// This tells us how many list items we can retrieve.
clientContext.Load(clientContext.Site,
s => s.MaxItemsPerThrottledOperation);
clientContext.ExecuteQuery();
// Let's just pick the first View.
View targetView = externalList.Views[0];
string method = ReadMethodFromViewXml(
targetView.HtmlSchemaXml);
ViewFieldCollection viewFields = targetView.ViewFields;
CamlQuery vlQuery = CreateCamlQuery(
clientContext.Site.MaxItemsPerThrottledOperation,
method,
viewFields);
Expression<Func<ListItem, object>>[] listItemExpressions =
CreateListItemLoadExpressions(viewFields);
ListItemCollection listItemCollection =
externalList.GetItems(vlQuery);
// Note: Due to limitation, you currently cannot use
// ClientContext.Load.
// (you'll get InvalidQueryExpressionException)
IEnumerable<ListItem> resultData = clientContext.LoadQuery(
listItemCollection.Include(listItemExpressions));
clientContext.ExecuteQuery();
foreach (ListItem li in resultData)
{
// Now you can use the ListItem data!
// Note: In the CamlQuery, we specified RowLimit of
// MaxItemsPerThrottledOperation.
// You may want to check whether there are other rows
// not yet retrieved.
}
}
/// <summary>
/// Parses the viewXml and returns the Method value.
/// </summary>
private static string ReadMethodFromViewXml(string viewXml)
{
XmlReaderSettings readerSettings = new XmlReaderSettings();
readerSettings.ConformanceLevel = ConformanceLevel.Fragment;
XmlReader xmlReader = XmlReader.Create(
new StringReader(viewXml), readerSettings);
while (xmlReader.Read())
{
switch (xmlReader.NodeType)
{
case XmlNodeType.Element:
if (xmlReader.Name == "Method")
{
while (xmlReader.MoveToNextAttribute())
{
if (xmlReader.Name == "Name")
{
return xmlReader.Value;
}
}
}
break;
}
}
throw new Exception("Unable to find Method in View XML");
}
/// <summary>
/// Creates a CamlQuery based on the inputs.
/// </summary>
private static CamlQuery CreateCamlQuery(
uint rowLimit, string method, ViewFieldCollection viewFields)
{
CamlQuery query = new CamlQuery();
XmlWriterSettings xmlSettings = new XmlWriterSettings();
xmlSettings.OmitXmlDeclaration = true;
StringBuilder stringBuilder = new StringBuilder();
XmlWriter writer = XmlWriter.Create(
stringBuilder, xmlSettings);
writer.WriteStartElement("View");
// Specifies we want all items, regardless of folder level.
writer.WriteAttributeString("Scope", "RecursiveAll");
writer.WriteStartElement("Method");
writer.WriteAttributeString("Name", method);
writer.WriteEndElement(); // Method
if (viewFields.Count > 0)
{
writer.WriteStartElement("ViewFields");
foreach (string viewField in viewFields)
{
if (!string.IsNullOrEmpty(viewField))
{
writer.WriteStartElement("FieldRef");
writer.WriteAttributeString("Name", viewField);
writer.WriteEndElement(); // FieldRef
}
}
writer.WriteEndElement(); // ViewFields
}
writer.WriteElementString(
"RowLimit", rowLimit.ToString(CultureInfo.InvariantCulture));
writer.WriteEndElement(); // View
writer.Close();
query.ViewXml = stringBuilder.ToString();
return query;
}
/// <summary>
/// Returns an array of Expression used in
/// ClientContext.LoadQuery to retrieve
/// the specified field data from a ListItem.
/// </summary>
private static Expression<Func<ListItem, object>>[]
CreateListItemLoadExpressions(
ViewFieldCollection viewFields)
{
List<Expression<Func<ListItem, object>>> expressions =
new List<Expression<Func<ListItem, object>>>();
foreach (string viewFieldEntry in viewFields)
{
// Note: While this may look unimportant,
// and something we can skip, in actuality,
// we need this step. The expression should
// be built with local variable.
string fieldInternalName = viewFieldEntry;
Expression<Func<ListItem, object>>
retrieveFieldDataExpression =
listItem => listItem[fieldInternalName];
expressions.Add(retrieveFieldDataExpression);
}
return expressions.ToArray();
}
}
}