CAML（Collaborative Application Markup Language）——协作应用程序标记语言，在调用WSS提供的诸多Web Service时进行数据查询的一组XML规范，通过这种规范组织查询语句进行数据的检索。我在这里不想再具体介绍CAML的使用规范和具体语法了，读者在MSDN或者园子里的其它文章中都可以了解到。
http://msdn.microsoft.com/zh-cn/library/ms462365.aspx
http://www.cnblogs.com/shanqian/archive/2008/09/25/859513.html
这里我想给出我在项目实际应用中所积累的有关使用CAML查询语句时所解决的问题。
1. Sharepoint的List中允许创建Document和Folder两种类型的数据，在查询时如何查出非Folder类型的数据？
2 < Where >
3 < Neq >
4 < FieldRef Name ="ContentType" />
5 < Value Type ="Text" > Folder </ Value >
6 </ Neq >
7 </ Where >
8 </ Query >
当服务器上安装有WSS的多语言包时，根据不同的语言ContentType的值也会有不同的写法，可以借助CAML工具或者在WSS查询返回的报文中查看一下，确认ContentType的具体类型名称。
2. 如何查询List中Lookup类型的字段的值？
Loopup类型的字段在数据库中相当于外键，数据格式如1;#title1;#2;#title2，查询时可以按照下面的CAML。
2 < Where >
3 < Eq >
4 < FieldRef Name ="ProjectID" />
5 < Value Type ="Lookup" > My Test Project 1 </ Value >
6 </ Eq >
7 </ Where >
8 </ Query >
2 < Where >
3 < Eq >
4 < FieldRef Name ="ProjectID" LookupId ="TRUE" />
5 < Value Type ="Text" > 3 </ Value >
6 </ Eq >
7 </ Where >
8 </ Query >
3. Lists.GetListItems()方法中的参数。
对于该方法中参数的详解，读者可以参考MSDN：
http://msdn.microsoft.com/zh-cn/library/websvclists.lists.getlistitems.aspx
这里对参数的几点用法做一些说明：
| listName | 要查询的List的名称，也可以为List的GUID，不能为空。 |
| viewName | 一般都为空。 |
| query | 标准CAML查询语句，可以为空，<Query></Query> |
| viewFields | 要查询的字段，可以为空，<ViewFields></ViewFields> |
| rowLimit | 返回的记录条数，默认为100，如果不需要限制，将值设为0 。 |
| queryOptions | 查询选项设置，所涉及到的选项比较多，可以参考MSDN。 http://msdn.microsoft.com/zh-cn/library/websvclists.lists.getlistitems.aspx 如果要查询List中Folder下的文档，则必须添加递归选项。 <QueryOptions> <ViewAttributes Scope="Recursive" /> |
| webID | 可选参数。具体用法查看MSDN。 |
List的GUID可以通过调用Lists.GetListAndView()方法，在返回的报文中获取到。
http://msdn.microsoft.com/zh-cn/library/websvclists.lists.getlistandview.aspx
4. 搜集到的List中字段的属性，包括字段的Type。
| ID | The ID is a globally unique identifier (GUID) which you should generate for each field. This ID will be used in lists when referencing the site column | |
| Type | The type indicates the data type of the column and can be of the any following: | |
| AllDayEvent | The all day event flag is used in calendar lists. | |
| Attachments | The URL of an attachment. | |
| Boolean | A boolean indicator with Yes/No. | |
| Calculated | Indicates that the column is a calculated column based on a expression. | |
| Choice | Indicates that the column is choice from a list of items | |
| Computed | Indicates the field's value is dependant on another field's value. | |
| ContentTypeId | A Content Type ID value. | |
| Counter | An internal unique ID's / counter for each item. | |
| Currency | A currency value (its format depends on the locale). | |
| DateTime | A Date and Time field. | |
| File | A file object when used in document libraries. | |
| GridChoice | A rating scale as used in surveys | |
| Guid | A globally unique identifier. | |
| Integer | An integer number field. | |
| Lookup | The field is a lookup which is a choice, however the choice is from another list. | |
| LookupMulti | A lookup field, however multiple selections are allowed. | |
| ModStat | An approval status. | |
| MultiChoice | A choice field, however multiple selections are allowed | |
| Note | Multiple lines of text which can be plain or formatted. | |
| Number | A numerical field which allows decimal places. | |
| PageSeparator | A page separator field, for surveys. | |
| Recurrence | An indicator that identifies the field as a reoccurring calendar event. | |
| Text | A single line of text | |
| ThreadIndex | The ID of a discussion thread. | |
| Threading | Indicates the field supports threading (in discussions). | |
| URL | A Unified Resource Locator (URL) is stored. | |
| User | A person or group. | |
| UserMulti | A person or group, however multiple people or groups can be selected. | |
| WorkflowEventType | Contains the type of workflow history event (used in workflow history list). | |
| WorkflowStatus | The status of a workflow is stored. | |
| Title | The name of the field as displayed in the user interface. This title may be set using a resource file. | |
| Name | (optional) The name of the field which should be guaranteed to never change. The default is the Title with spaces and invalid characters removed. | |
| StaticName | (optional) The logical name of the field which is similar to Name, however this can be programmatically changed. | |
| DisplayName | (optional) See title. | |
| Description | (optional) A description of the field which will be displayed in front ends. The description can be placed into a resource file. | |
| Required | (optional) Indicates whether or not the field is mandatory. The default is FALSE. | |
| MaxLength | (optional) The maximum number of characters allowed. | |
| Hidden | (optional) Indicates that the field should be hidden from the interface. If TRUE, this field will not be shown on views or forms. The default is FALSE. | |
| Readonly | (optional) The field should be read-only and can be displayed and not edited. The default is FALSE. | |
| ShowInDisplayForm | (optional) Indicates whether the field should be shown on a display form. The default is TRUE. | |
| ShowInEditForm | (optional) Indicates whether the field should be shown on an edit form. The default is TRUE. | |
| ShowInListSettings | (optional) Indicates whether the field should be shown in the list settings screen. The default is TRUE. | |
| ShowInNewForm | (optional) Indicates whether the field should be shown on a New form. The default is TRUE. | |
| ShowInVersionHistory | (optional) Indicates whether the field should be shown in the version history of an item. The default is TRUE. | |
| ShowInViewForms | (optional) Indicates whether the field should be shown on a view form. The default is TRUE. | |
| Group | (optional) A group name allowing you to group fields together. | |
5. Customer List中的列名变化？
在Customer List中创建一个新列时，Sharepoint同时给它赋予了内部名称（FieldInternalName）和外部名称（FieldName），初始状态下内部名称和外部名称是相同的，当我们修改了List的列名时，外部名称被修改了，而内部名称则不变，为了防止在使用时出现找不到列的错误，必须在CAML中使用内部名称作为列名。可以借助CAML工具查找列的内部名称，也可以在List的新建记录页面中查看源代码，搜索显示的列名，找到类似于下面的代码段，FieldInternalName的值即为该列的内部名称。
FieldInternalName="Title"
FieldType="SPFieldText"
-->
6. 两个小工具，用于检测或生成CAML，对List的管理和查看报文的具体信息。实际项目应用中会很有用哦:)
U2U Caml Query Builder 2007 v3.1.0.0 (windows version)
CAML的使用过程中还是会遇到很多问题的，以后遇到再逐渐补上吧！
本文转自Jaxu博客园博客，原文链接：http://www.cnblogs.com/jaxu/archive/2009/03/23/1419717.html，如需转载请自行联系原作者
