Connection 对象表示数据库连接或类似的资源，它是 .NET 数据提供程序用户的起点。虽然任何具有类似行为的实体都可以公开为 IDbConnection，但该对象主要表示与数据库服务器的连接。

在您的实现中，必须确保先创建和打开 Connection，然后才可以执行 Command。请确保您的实现要求客户端显式打开和关闭连接，而不是让实现为客户端隐式打开和关闭连接。在获取连接时应执行安全检查；如果为 .NET 数据提供程序中的其他类请求现有连接，则将确保每次使用数据源时都会执行安全检查。

所需连接的属性将表示为连接字符串。强烈建议 .NET 数据提供程序使用 OLE DB 所定义的常见名称/值对系统来支持 ConnectionString 属性。只要可能，提供程序就应该使用与 SQL Server 和 OLE DB .NET 数据提供程序所使用的相同名称来引用连接属性。这有助于确保多个提供程序之间的一致性。有关更多信息，请参阅位于 http://msdn.microsoft.com/library 的 MSDN 库中的 SqlConnection.ConnectionString 属性 和“OLE DB 编程指南”。

获取 Connection 对象的成本通常很昂贵，因此最好考虑使用池连接或其他技术来减轻此项费用。

IDbConnection 的实现至少应包含两个构造函数：一个默认的构造函数和一个采用连接字符串的构造函数。

以下主题包含 Connection 对象的实现的示例代码。

对于示例 Visual Basic 实现：

• TemplateConnection.vb(略)
• TemplateTransaction.vb(略)

对于示例 C# 实现：

• TemplateConnection.cs

  using System; using System.Data; namespace DotNetDataProviderTemplate {   public class TemplateConnection : IDbConnection   {     private ConnectionState m_state;     private string      m_sConnString;     // Use the "SampleDb" class to simulate a database connection.     SampleDb m_sampleDb;     // Always have a default constructor.     public TemplateConnection()     {       // Initialize the connection object into the closed state.       m_state = ConnectionState.Closed;       /*        * Obtain a connection to the database. In this case,        * use the SampleDb class to simulate a connection to        * a real database.        */       m_sampleDb = new SampleDb();     }         // Have a constructor that takes a connection string.     public TemplateConnection(string sConnString)     {       // Initialize the connection object into a closed state.       m_state = ConnectionState.Closed;     }     /****      * IMPLEMENT THE REQUIRED PROPERTIES.      ****/     public string ConnectionString     {       get       {         // Always return exactly what the user set.         // Security-sensitive information may be removed.         return m_sConnString;       }       set       {         m_sConnString = value;       }     }     public int ConnectionTimeout     {       get       {         // Returns the connection time-out value set in the connection         // string. Zero indicates an indefinite time-out period.         return 0;       }     }     public string Database     {       get       {         // Returns an initial database as set in the connection string.         // An empty string indicates not set - do not return a null reference.         return "";       }     }     public ConnectionState State     {       get { return m_state; }     }     /****      * IMPLEMENT THE REQUIRED METHODS.      ****/     public IDbTransaction BeginTransaction()     {       throw new NotSupportedException();     }     public IDbTransaction BeginTransaction(IsolationLevel level)     {       throw new NotSupportedException();     }     public void ChangeDatabase(string dbName)     {       /*        * Change the database setting on the back-end. Note that it is a method        * and not a property because the operation requires an expensive        * round trip.        */     }     public void Open()     {       /*        * Open the database connection and set the ConnectionState        * property. If the underlying connection to the server is        * expensive to obtain, the implementation should provide        * implicit pooling of that connection.        *        * If the provider also supports automatic enlistment in        * distributed transactions, it should enlist during Open().        */       m_state = ConnectionState.Open;     }     public void Close()     {       /*        * Close the database connection and set the ConnectionState        * property. If the underlying connection to the server is        * being pooled, Close() will release it back to the pool.        */       m_state = ConnectionState.Closed;     }     public IDbCommand CreateCommand()     {       // Return a new instance of a command object.       return new TemplateCommand();     }     /*      * Implementation specific properties / methods.      */     internal SampleDb SampleDb     {       get { return m_sampleDb; }     }   } }

• TemplateTransaction.cs

  using System; using System.Data; namespace DotNetDataProviderTemplate {   public class TemplateTransaction : IDbTransaction   {     public IsolationLevel IsolationLevel     {       /*        * Should return the current transaction isolation        * level. For the template, assume the default        * which is ReadCommitted.        */       get { return IsolationLevel.ReadCommitted; }     }     public void Commit()     {       /*        * Implement Commit here. Although the template does        * not provide an implementation, it should never be        * a no-op because data corruption could result.        */     }     public void Rollback()     {       /*        * Implement Rollback here. Although the template does        * not provide an implementation, it should never be        * a no-op because data corruption could result.        */     }   } }