我有一个名为DatabaseHelper的类,它包装了一个DbConnection。为using语句设置此类的正确方法是什么?我已经实现了IDisposible,但我不确定我应该何时何地调用Connection.Close()或Connection.Dispose()。
当我在我自己的Dispose()方法中调用Connection.Dispose()时,我有时会从DbConnection对象中获取SocketException。我认为这是因为旧的连接处于打开状态,但是没有附加到异常的详细信息,所以我无法确定。
答案 0 :(得分:6)
从您的dispose方法中调用connection.Dispose()。您应该看一下实现IDisposable的标准模式,它超越了简单地实现IDisposable接口并允许处理非托管对象等:
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (!disposed)
{
if (disposing)
{
// Dispose managed resources.
}
// There are no unmanaged resources to release, but
// if we add them, they need to be released here.
}
disposed = true;
// If it is available, make the call to the
// base class's Dispose(Boolean) method
base.Dispose(disposing);
}
(取自http://msdn.microsoft.com/en-us/library/system.idisposable.aspx)。
答案 1 :(得分:2)
根据this新闻组:
以下是IDbConnection.Dispose()的实现方式(如Reflector实用程序所示):
的SqlClient:
protected override void Dispose(bool disposing)
{
if (disposing)
{
switch (this._objectState)
{
case ConnectionState.Open:
{
this.Close();
break;
}
}
this._constr = null;
}
base.Dispose(disposing);
}
Odbc:
protected override void Dispose(bool disposing)
{
if (disposing)
{
this._constr = null;
this.Close();
CNativeBuffer buffer1 = this._buffer;
if (buffer1 != null)
{
buffer1.Dispose();
this._buffer = null;
}
}
base.Dispose(disposing);
}
OleDb:
protected override void Dispose(bool disposing)
{
if (disposing)
{
if (this.objectState != 0)
{
this.DisposeManaged();
if (base.DesignMode)
{
OleDbConnection.ReleaseObjectPool();
}
this.OnStateChange(ConnectionState.Open, ConnectionState.Closed);
}
if (this.propertyIDSet != null)
{
this.propertyIDSet.Dispose();
this.propertyIDSet = null;
}
this._constr = null;
}
base.Dispose(disposing);
}
您的dispose方法只应尝试在连接打开时关闭连接。
答案 2 :(得分:1)
这个析构函数语法实际上是终结器。终结器调用Dispose(false) 方法
#region IDisposable Members
private bool _isDisposed;
private void ThrowIfDisposed()
{
if (_isDisposed)
throw new ObjectDisposedException(this.GetType().Name);
}
protected virtual void Dispose(bool disposing)
{
if (!_isDisposed)
{
if (disposing)
{
//part 1 : disposing managed objects
_command.Dispose();
_command.Connection.Dispose();
if (_command.Transaction != null)
_command.Transaction.Dispose();
}
//part 2: disposing unmanged objects. Here there are no unmanged objects.
_isDisposed = true;
}
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
//~DbCommandExecutor() //No need of finalize here. Because there is no unmanged objects in my class. ie, no code in part 2.
//{
// Dispose(false);
//}
#endregion
在您的代码具有第2部分代码之前,不需要终结器(或析构函数)语法。否则应该为安全起见而实施。即,即使程序员没有正确调用dispose方法,finalize也应该清理非托管资源。
比较示例:来自msdn
http://msdn.microsoft.com/en-us/library/system.idisposable.dispose.aspx& http://msdn.microsoft.com/en-us/library/fs2xkftw.aspx
答案 3 :(得分:0)
只是为了完成IDisposable实现模式,通常为您的类包含一个终结器(析构函数),它调用Dispose()方法(传递false)。这充当故障保护机制,如果类的使用者无法调用Dispose(),则允许您处置非托管对象。
~MyClass()
{
Dispose(false);
}