很多人都认为Close()方法内部会调用Dispose()方法，所以并没有本质的区别！实际上这个看法不是很准确，对有些类来说，的确Close()和Dispose()没有本质区别，但是对有些类来说并非如此！
首先，让我们看看我们最常使用的SqlConnection的Close()方法和Dispose()方法的区别：
SqlConnection类的Dispose()方法是继承于Component类的，源代码是这样的：
public void Dispose() {
Dispose(true); //调用Dispose的一个带参数的重载
GC.SuppressFinalize(this); //请求系统不要调用指定对象的终结器。
}
protected virtual void Dispose(bool disposing) {
if (disposing) {
lock(this) {
if (site != null && site.Container != null) {
site.Container.Remove(this);
}
if (events != null) {
EventHandler handler = (EventHandler)events[EventDisposed];
if (handler != null) handler(this, EventArgs.Empty);
}
}
}
}
SqlConnection类的Close()方法在MSDN中的说明是这样的：
关闭与数据库的连接。这是关闭任何打开连接的首选方法。 如果 SqlConnection 超出范围，则不会将其关闭。因此，必须通过调用 Close 或 Dispose 显式关闭该连接。Close 和 Dispose 在功能上等效。如果连接池值Pooling 设置为 true 或 yes，则基础连接将返回到连接池。另一方面，如果 Pooling 设置为 false 或 no，则会关闭到服务器的基础连接。
看说明好象是Close()方法和Dispose()方法是类似的，实际上只是在关闭连接这个功能上等效，让我们看看Close()方法的源代码：
override public void Close() {
IntPtr hscp;
Bid.ScopeEnter(out hscp, "<sc.SqlConnection.Close|API> %d#" , ObjectID);
try {
SqlStatistics statistics = null;
RuntimeHelpers.PrepareConstrainedRegions();
try {
#if DEBUG
object initialReliabilitySlotValue = Thread.GetData(TdsParser.ReliabilitySlot);
RuntimeHelpers.PrepareConstrainedRegions();
try {
Thread.SetData(TdsParser.ReliabilitySlot, true);
#endif //DEBUG
statistics = SqlStatistics.StartTimer(Statistics);
// The lock here is to protect against the command.cancel / connection.close
race condition
// The SqlInternalConnectionTds is set to OpenBusy during close, once this
happens the cast below will fail and
// the command will no longer be cancelable. It might be desirable to be
able to cancel the close opperation, but this is
// outside of the scope of Whidbey RTM. See (SqlCommand::Cancel) for other
lock.
lock (InnerConnection) {
InnerConnection.CloseConnection(this, ConnectionFactory);
}
// does not require GC.KeepAlive(this) because of OnStateChange
if (null != Statistics) {
ADP.TimerCurrent(out _statistics._closeTimestamp);
}
#if DEBUG
}
finally {
Thread.SetData(TdsParser.ReliabilitySlot, initialReliabilitySlotValue);
}
#endif //DEBUG
}
catch (System.OutOfMemoryException e) {
Abort(e);
throw;
}
catch (System.StackOverflowException e) {
Abort(e);
throw;
}
catch (System.Threading.ThreadAbortException e) {
Abort(e);
throw;
}
finally {
SqlStatistics.StopTimer(statistics);
}
}
finally {
SqlDebugContext sdc = _sdc;
_sdc = null;
Bid.ScopeLeave(ref hscp);
if (sdc != null) {
sdc.Dispose();
}
}
}