如果一个类型实现了IDispose接口,但是在退出作用域前未Disposed/Close, 代码分析工具会提出警告:
CA2000: Dispose objects before losing scope
例如:
public string OpenPort1(string portName){
SerialPort port = new SerialPort(portName); //SerialPort实现了IDispose接口
port.Open(); //CA2000 fires because this might throw
SomeMethod(); //Other method operations can fail
return port.ToString();
}
如果SomeMethod出现异常,此类型也会安全释放未托管资源.如果用using包装,则不会有此警告.
public string OpenPort1(string portName)
{
string result = string.Emtpy;
using(SerialPort port = new SerialPort(portName))
{
port.Open(); //CA2000 fires because this might throw
SomeMethod(); //Other method operations can fail,
result = port.ToString();
}
return result;
}
当此类型作为返回值时,不能直接采用using来释放资源,如下例:
public SerialPort OpenPort1(string portName)
{
SerialPort port = new SerialPort(portName); port.Open(); //CA2000 fires because this might throw
SomeMethod(); //Other method operations can fail return port;
return port;
}
为避免操作中出现异常导致未托管资源未释放, 可采用try/finally包装代码,以保证在异常时资源安全释放,如下:
public SerialPort OpenPort2(string portName)
{
SerialPort tempPort = null;
SerialPort port = null;
try
{
tempPort = new SerialPort(portName);
tempPort.Open();
SomeMethod();
//Add any other methods above this line
port = tempPort;
tempPort = null;
}
finally
{
if (tempPort != null)
{
tempPort.Close();
}
}
return port;
}
Detail See MSDN:CA2000: Dispose objects before losing scope