C# 使用IDisposable处理对象是否正确
我有一个实现IDisposable接口的类。我正在使用webclient使用AsyncDownloadString下载一些数据 我想知道我是否在构造函数和web客户端的using语句中正确声明了事件处理程序？这是删除Dispose方法中的事件处理程序的正确方法吗 否决这是使用IDisposable接口的正确方法吗C# 使用IDisposable处理对象是否正确,c#,idisposable,C#,Idisposable,我有一个实现IDisposable接口的类。我正在使用webclient使用AsyncDownloadString下载一些数据 我想知道我是否在构造函数和web客户端的using语句中正确声明了事件处理程序？这是删除Dispose方法中的事件处理程序的正确方法吗 否决这是使用IDisposable接口的正确方法吗 public class Balance : IDisposable { //Constructor WebClient wc; public Balance(
public class Balance : IDisposable
{
//Constructor
WebClient wc;
public Balance()
{
using (wc = new WebClient())
{
//Create event handler for the progress changed and download completed events
wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
}
}
~Balance()
{
this.Dispose(false);
}
//Get the current balance for the user that is logged in.
//If the balance returned from the server is NULL display error to the user.
//Null could occur if the DB has been stopped or the server is down.
public void GetBalance(string sipUsername)
{
//Remove the underscore ( _ ) from the username, as this is not needed to get the balance.
sipUsername = sipUsername.Remove(0, 1);
string strURL =
string.Format("https://www.xxxxxxx.com",
sipUsername);
//Download only when the webclient is not busy.
if (!wc.IsBusy)
{
// Download the current balance.
wc.DownloadStringAsync(new Uri(strURL));
}
else
{
Console.Write("Busy please try again");
}
}
//return and display the balance after the download has fully completed
void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
//Pass the result to the event handler
}
//Dispose of the balance object
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
//Remove the event handlers
private bool isDisposed = false;
private void Dispose(bool disposing)
{
if (!this.isDisposed)
{
if (disposing)
{
wc.DownloadProgressChanged -= new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
wc.DownloadStringCompleted -= new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
wc.Dispose();
}
isDisposed = true;
}
}
}
这基本上是正确的，除了
wcGetBalancewcpublic class Balance : IDisposable
{
//Constructor
WebClient wc;
public Balance()
{
wc = new WebClient();
//Create event handler for the progress changed and download completed events
try {
wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
} catch {
wc.Dispose();
throw;
}
}
~Balance()
{
this.Dispose(false);
}
//Get the current balance for the user that is logged in.
//If the balance returned from the server is NULL display error to the user.
//Null could occur if the DB has been stopped or the server is down.
public void GetBalance(string sipUsername)
{
//Remove the underscore ( _ ) from the username, as this is not needed to get the balance.
sipUsername = sipUsername.Remove(0, 1);
string strURL =
string.Format("https://www.xxxxxxx.com",
sipUsername);
//Download only when the webclient is not busy.
if (!wc.IsBusy)
{
// Download the current balance.
wc.DownloadStringAsync(new Uri(strURL));
}
else
{
Console.Write("Busy please try again");
}
}
//return and display the balance after the download has fully completed
void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
//Pass the result to the event handler
}
private bool isDisposed = false;
//Dispose of the balance object
public void Dispose()
{
if (!isDisposed)
Dispose(true);
GC.SuppressFinalize(this);
}
//Remove the event handlers
private void Dispose(bool disposing)
{
isDisposed = true;
if (disposing)
{
wc.DownloadProgressChanged -= new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
wc.DownloadStringCompleted -= new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
wc.Dispose();
}
}
}
这基本上是正确的，除了
wcGetBalancewcpublic class Balance : IDisposable
{
//Constructor
WebClient wc;
public Balance()
{
wc = new WebClient();
//Create event handler for the progress changed and download completed events
try {
wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
} catch {
wc.Dispose();
throw;
}
}
~Balance()
{
this.Dispose(false);
}
//Get the current balance for the user that is logged in.
//If the balance returned from the server is NULL display error to the user.
//Null could occur if the DB has been stopped or the server is down.
public void GetBalance(string sipUsername)
{
//Remove the underscore ( _ ) from the username, as this is not needed to get the balance.
sipUsername = sipUsername.Remove(0, 1);
string strURL =
string.Format("https://www.xxxxxxx.com",
sipUsername);
//Download only when the webclient is not busy.
if (!wc.IsBusy)
{
// Download the current balance.
wc.DownloadStringAsync(new Uri(strURL));
}
else
{
Console.Write("Busy please try again");
}
}
//return and display the balance after the download has fully completed
void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
//Pass the result to the event handler
}
private bool isDisposed = false;
//Dispose of the balance object
public void Dispose()
{
if (!isDisposed)
Dispose(true);
GC.SuppressFinalize(this);
}
//Remove the event handlers
private void Dispose(bool disposing)
{
isDisposed = true;
if (disposing)
{
wc.DownloadProgressChanged -= new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
wc.DownloadStringCompleted -= new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
wc.Dispose();
}
}
}
有两种正确的方法可以使用IDisposable对象：
块将其放入中
或
块创建的在这里，当您使用构造函数中的
块创建WebClient实例时，在您有机会在任何其他地方使用它之前，您会先处理它。在这种情况下，您应该只执行选项二。使用IDisposable对象有两种正确的方法：
使用块将其放入中
或
将它包装在一个类中，该类也正确实现IDisposable，并在释放这个新类时释放它。现在，您希望新类的所有实例都是使用块创建的
请注意，我说的是“或”，而不是“和”。做一个或另一个，但不能同时做两个
在这里，当您使用构造函数中的块创建WebClient实例时，在您有机会在任何其他地方使用它之前，您会先处理它。在这种情况下，您应该只执行选项二。因为您在using语句中声明了wc，所以不应该在using语句之外使用。所以我猜在GetBalance中使用wc的调用会抛出异常。
您应该从Balance Constructor中删除using块
有关using语句的更多信息，请参见“”。由于您已在using语句内声明了wc，因此不应在using语句外使用wc。所以我猜在GetBalance中使用wc的调用会抛出异常。
您应该从Balance Constructor中删除using块
有关using语句的更多信息，请参见“”。其他答案是正确的，但它们都忽略了一个事实，即您正在声明终结器，而您不应该这样做
根据.Net Framework设计指南（第258页）：
- 避免使类型可终结
- 如果类型负责释放没有自己终结器的非托管资源，则执行使类型可终结
因此，rpetrich的已编辑答案是正确的，如果有人具有编辑权限，则会删除终结器。其他答案是正确的，但它们都忽略了一个事实，即您正在声明终结器，而您不应该声明终结器
根据.Net Framework设计指南（第258页）：
- 避免使类型可终结
- 如果类型负责释放没有自己终结器的非托管资源，则执行使类型可终结
因此，rpetrich的编辑答案是正确的，如果有人具有编辑权限，则会删除终结器。出于好奇，放置：wc.DownloadProgressChanged-=new DownloadProgressChangedEventHandler（wc\u DownloadProgressChanged）会有问题吗；wc.DownloadStringCompleted-=新的DownloadStringCompletedEventHandler（wc_DownloadStringCompleted）；在析构函数中，而不是在Dispose中？（因为这些不是非托管对象）？dispose是否会使对象无效，因此您需要在此处执行这些操作？IDisposable
是一种实现资源确定性处置的模式。应该清理Dispose方法中的所有资源——一旦它运行，终结器将被抑制。终结器应该运行的唯一时间是对象未正确处置的情况。删除事件处理程序的主要原因是，我们可以确定在处理对象后不会收到wc\u DownloadStringCompleted
；这是出乎意料的。Zenox，除非必须，否则永远不应该实现终结器-它只是用于清理非托管内存。您肯定不想引用终结器中的其他对象，因为不能保证它们尚未被释放/终结。请参阅下面我的答案&有关更长的答案，请掌握框架设计指南。基本上，您应该始终询问是否需要终结器，并非常仔细地检查它的功能。来自终结器的未处理异常会立即导致应用程序崩溃，无法恢复（它如何恢复，它在自己的线程中运行）。您应该删除终结器/析构函数。它不属于您，您也不需要它，因为内置在现有webclient类型中的终结器仍将运行并负责处理该对象。出于好奇，放置：wc.DownloadProgressChanged-=new DownloadProgressChangedEventHandler（wc_DownloadProgressChanged）会有问题吗；wc.DownloadStringCompleted-=新的DownloadStringCompletedEventHandler（wc_DownloadStringCompleted）；在析构函数中，而不是在Dispose中？（因为这些不是非托管对象）？是指dispose可能使对象无效的问题，