ADO.NET：连接池

此示例阐释如何建立到数据源的连接池。需要进行此操作来部署高性能的应用程序。在此示例中，池是在连接字符串中建立起来，并由 SqlConnection 自动管理的。

VB ConnectionPooling.aspx [运行示例] | [查看源代码]

在此示例中，在构造 SqlConnection 时在连接字符串中指定池特性，如以下的代码示例中所示。请注意：池处理是隐式的，除非将其禁用，否则将自动进行池处理。因此，"true"是默认的池关键词 (pooling=true)。

String connString;// Specification in the connection string:// Please note: Pooling is implicit, you automatically get it unless you disable it. // Therefore, "true" is the default for the pooling keyword (pooling=true). // Connection Reset: False// Connection Lifetime: 5// Enlist: true// Min Pool Size: 1// Max Pool Size: 50connString = "server=(local)//VSdotNET;Trusted_Connection=yes;database=northwind;" + "connection reset=false;" + "connection lifetime=5;" + "min pool size=1;" + "max pool size=50";SqlConnection myConnection1 = new SqlConnection(connString);SqlConnection myConnection2 = new SqlConnection(connString);SqlConnection myConnection3 = new SqlConnection(connString); Dim connString as String' Specification in the connection string:' Please note: Pooling is implicit, you automatically get it unless you disable it. ' Therefore, "true" is the default for the pooling keyword (pooling=true). ' Connection Reset: False' Connection Lifetime: 5' Enlist: true' Min Pool Size: 1' Max Pool Size: 50connString = "server=(local)/VSdotNET;Trusted_Connection=yes;database=northwind;" & _ "connection reset=false;" & _ "connection lifetime=5;" & _ "enlist=true;" & _ "min pool size=1;" & _ "max pool size=50"Dim myConnection1 as SqlConnection = new SqlConnection(connString)Dim myConnection2 as SqlConnection = new SqlConnection(connString)Dim myConnection3 as SqlConnection = new SqlConnection(connString)
C#	VB

现在，我们有了使用池中的若干连接的代码。首先，打开两个连接并返回这两个到池的连接。然后，从池中打开三个连接，并返回所有这三个到池的连接。

// Open two connections. One is from the pool (see min pool size), the other is created.Console.WriteLine ("Open two connections.");myConnection1.Open();myConnection2.Open();// Now there are two connections in the pool that matches the connection string.// Return the both connections to the pool. Console.WriteLine ("Return both of the connections to the pool.");myConnection1.Close();myConnection2.Close();// Get a connection out of the pool.Console.WriteLine ("Open a connection from the pool.");myConnection1.Open();// Get a second connection out of the pool.Console.WriteLine ("Open a second connection from the pool.");myConnection2.Open();// Open a third connection.Console.WriteLine ("Open a third connection.");myConnection3.Open();// Return the all connections to the pool. Console.WriteLine ("Return all three connections to the pool.");myConnection1.Close();myConnection2.Close();myConnection3.Close(); ' Open two connections. One is from the pool (see min pool size), the other is created.Console.WriteLine ("Open two connections.")myConnection1.Open()myConnection2.Open()' Now there are two connections in the pool that matches the connection string.' Return the both connections to the pool. Console.WriteLine ("Return both of the connections to the pool.")myConnection1.Close()myConnection2.Close()' Get a connection out of the pool.Console.WriteLine ("Open a connection from the pool.")myConnection1.Open()' Get a second connection out of the pool.Console.WriteLine ("Open a second connection from the pool.")myConnection2.Open()' Open a third connection.Console.WriteLine ("Open a third connection.")myConnection3.Open()' Return the all connections to the pool. Console.WriteLine ("Return all three connections to the pool.")myConnection1.Close()myConnection2.Close()myConnection3.Close()
C#	VB

池连接的模型与非池连接的相似。但是，当断开池连接来将其释放回池时，调用 Close 是特别重要的。