ADO对象模型的概要.doc资源-CSDN文库

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ADO（ActiveX Data Objects）是Microsoft开发的一种数据访问接口，用于与各种数据源进行交互，如数据库、XML文件等。ADO对象模型是一个组件化的结构，它由多个对象组成，每个对象都有特定的功能，使得开发者能够方便地执行数据操作。下面我们将详细探讨这些对象及其主要属性和方法。 1. **Command对象**：Command对象用于定义要对数据源执行的具体命令，如SQL查询或存储过程。它允许设置命令文本、参数和命令类型。`CommandText`属性用于设定命令的文本，`Parameters`集合用于添加和管理与命令相关的参数。 2. **Connection对象**：Connection对象表示到数据源的开放连接。它允许用户建立和关闭连接，并执行事务。`ConnectionString`属性用于指定连接字符串，`Open`方法用于打开连接，`Close`方法用于关闭连接。 3. **DataControl对象（RDS）**：在Web页面上，DataControl对象将数据查询的Recordset绑定到一个或多个控件，如文本框、网格控件或组合框，以显示Recordset数据。 4. **DataFactory对象（RDSServer）**：为客户端应用程序提供对指定数据源的读写数据访问实现。 5. **DataSpace对象（RDS）**：创建客户端代理，以访问位于中间层的自定义业务对象。 6. **Error对象**：Error对象包含了针对提供者相关操作失败的所有错误细节。`Errors`集合包含了所有因操作失败产生的错误对象。 7. **Field对象**：Field对象代表Recordset中的列，具有相同的数据类型。`Name`属性表示字段名称，`Value`属性则为字段的当前值。 8. **Parameter对象**：Parameter对象与Command对象关联，表示基于参数化查询或存储过程的参数或参数。`Name`和`Value`属性分别代表参数名和参数值。 9. **Property对象**：Property对象表示由提供者定义的ADO对象的动态特性。例如，`Connect`属性是Connection对象的属性，用于获取或设置连接字符串。 10. **Record对象**：Record对象代表Recordset中的一行记录，或者文件系统中的一个目录或文件。`Fields`集合包含Record中的所有Field对象。 11. **Recordset对象**：Recordset对象表示基础表的全部记录或执行命令的结果。任何时候，Recordset对象都指向集合中的单个记录作为当前记录。`CursorLocation`属性设置游标的位置，`MoveFirst`、`MoveNext`、`MovePrevious`和`MoveLast`方法用于移动记录指针。 12. **Stream对象**：Stream对象代表二进制数据流，可以用于读取和写入大量二进制数据，如图像或文件。 13. **Collection对象**： - `Errors`集合包含所有由于提供者相关故障产生的Error对象。 - `Fields`集合包含Recordset对象的所有Field对象。 - `Parameters`集合包含Command对象的所有Parameter对象。 - `Properties`集合包含特定对象实例的所有Property对象。以上就是ADO对象模型的基本概览，通过这些对象，开发者可以实现与数据源的交互，包括查询、更新、删除和插入数据，以及处理错误和连接管理。在实际编程中，根据需求组合使用这些对象和它们的方法、属性，可以构建出强大的数据访问功能。

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ADO对象模型的概要
下图是ADO模型中的对象示意图，白色的是Collection。
ADO Object Summary
Object Description
Command Denes a specic command that you intend to execute against
a data source.
Connection Represents an open connection to a data source.
DataControl (RDS) Binds   a   data   query   Recordset   to   one   or   more   controls   (for
example, a text box, grid control, or combo box) to display the
Recordset data on a Web page.
DataFactory   (RDS
Server)
Implements   methods   that   provide   read/write   data   access   to
specied data sources for client-side applications.
DataSpace (RDS) Creates client-side proxies to custom business objects located
on the middle tier.
Error Contains details about data access errors that pertain to a single
operation involving the provider.
Field Represents a column of data with a common data type.
Parameter Represents   a   parameter   or   argument   associated   with   a
Command   object   based   on   a   parameterized   query   or   stored
procedure.
Property Represents a dynamic characteristic  of   an  ADO   object that is
dened by the provider.
Record Represents a row of a Recordset, or a directory or le in a le
system.

Recordset Represents the entire set of records from a base table  or the
results of  an   executed command. At any   time,   the Recordset
object refers to only a single record within the set as the current
record.
Stream Represents a binary stream of data.
ADO Collection Summary
Collection Description
Errors Contains   all  the   Error  objects   created   in  response  to  a   single  provider-
related failure.
Fields Contains all the Field objects of a Recordset object.
Parameters Contains all the Parameter objects of a Command object.
Properties Contains all the Property objects for a specic instance of an object.
ADO Property Summary
Property Description
AbsolutePage Indicates on which page the current record resides.
AbsolutePosition Indicates the ordinal position of a Recordset object's current record.
ActiveCommand Indicates the Command object that created the associated Recordset
object.
ActiveConnectio
n
Indicates   to   which   Connection   object   the   specied   Command,
Recordset, or Record object currently belongs.
ActualSize Indicates the actual length of a eld's value.
Attributes Indicates one or more characteristics of an object.
BOF and EOF BOF — indicates that the current record position is before the rst
record in a Recordset object.
EOF   —   indicates   that   the   current   record   position   is   after   the   last
record in a Recordset object.
Bookmark Indicates a bookmark that uniquely identies the current record in a
Recordset object or sets the current record in a Recordset object to
the record identied by a valid bookmark.
CacheSize Indicates   the  number  of  records   from  a  Recordset  object  that   are
cached locally in memory.
CharSet Indicates the character set into which the contents of a text Stream
should be translated.
CommandText Indicates the text of a command to be issued against a provider.
CommandTimeo
ut
Indicates   how   long   to   wait   while   executing   a   command   before
terminating the attempt and generating an error.
CommandType Indicates the type of a Command object.
Connect (RDS) Indicates   the   database   name   from   which   the   query   and   update
operations are run.

ConnectionStrin
g Property
Indicates the information   used to establish a connection  to  a data
source.
ConnectionTime
out
Indicates  how   long   to   wait  while   establishing   a   connection  before
terminating the attempt and generating an error.
Count Indicates the number of objects in a collection.
CursorLocation Indicates the location of the cursor service.
CursorType Indicates the type of cursor used in a Recordset object.
DataMember Indicates the name of the data member that will be retrieved from
the object referenced by the DataSource property.
DataSource Indicates   an   object   that   contains   data   to   be   represented   as   a
Recordset object.
DefaultDatabase Indicates the default database for a Connection object.
DenedSize Indicates the data capacity of a Field object.
Description Describes an Error object.
Direction Indicates whether the Parameter represents an input parameter, an
output parameter, or  both,   or if the parameter is the return  value
from a stored procedure.
EditMode Indicates the editing status of the current record.
EOS Indicates whether the current position is at the end of the stream.
ExecuteOptions
(RDS)
Indicates whether asynchronous execution is enabled.
FetchOptions
(RDS)
Indicates the type of asynchronous fetching.
Filter Indicates a lter for data in a Recordset.
FilterColumn
(RDS)
Indicates the column on which to evaluate the lter criteria.
FilterCriterion
(RDS)
Indicates the evaluation operator to use in the lter value.
FilterValue (RDS) Indicates the value to lter records.
Handler (RDS) Indicates the name of a server-side customization program (handler)
that extends the functionality of the RDSServer.DataFactory, and any
parameters used by the handler.
HelpContext and
HelpFile
Indicates the help le and topic associated with an Error object. 
HelpContextID — returns a context ID, as a Long value, for a topic in 
a Help le.
HelpFile — returns a String value that evaluates to a fully resolved 
path to a Help le. 
Index Indicates the name of the index currently in e6ect for a Recordset
object.
InternetTimeout Indicates the number of milliseconds to wait before a request times