C# 内存使用:Team Foundation Server dll 中流 class 使用的值与引用类型
C# memory usage: value vs reference type for stream class usage in Team Foundation Server dlls
我按照此处的示例 (How to attach a file to work item in TFS without physical file path?) 将文件附加到 TFS 中的工作项,方法是使用流而不是物理文件。我有以下代码:
internal static void AddAttachment(WorkItemServer server, Project teamProject, string fileContent, WorkItem workItem)
{
FileAttachment attachment = new FileAttachment();
using (MemoryStream stream = new MemoryStream())
{
using (StreamWriter writer = new StreamWriter(stream))
{
writer.Write(fileContent);
writer.Flush();
stream.Position = 0;
attachment.LocalFile = stream;
attachment.AreaNodeUri = "";
attachment.FileNameGUID = Guid.NewGuid();
attachment.ProjectUri = teamProject.Uri.ToString();
server.UploadFile(attachment);
const string c_UpdatePackage = @"<validxml>";
XmlDocument updatePackage = new XmlDocument();
updatePackage.LoadXml(string.Format(c_UpdatePackage, workItem.Id /*work item ID*/, workItem.Rev /*work item latest revision*/, "Test attachment", attachment.FileNameGUID, DateTime.Now.ToUniversalTime().ToString("yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fff'Z'"), fileContent.Length, "John Smith", "http://localhost:8080/tfs/defaultcollection"));
XmlElement outputPackage;
string dbStamp;
IMetadataRowSets metadata;
server.Update(Guid.NewGuid().ToString(), updatePackage.DocumentElement, out outputPackage, null, out dbStamp, out metadata);
}
}
}
我的问题:作业中
attachment.LocalFile = stream;
流是通过引用还是通过值复制到 attachment.LocalFile?如果它是通过引用复制的,我认为上面的代码不会有内存泄漏,因为它正在使用中处理流:
using (MemoryStream stream = new MemoryStream()) { ... }
但是如果它按值复制(制作流的副本),这将导致内存泄漏,因为 FileAttachment 没有被释放,对吧?如果存在内存泄漏,我认为无法修复此内存泄漏,因为 FileAttachment 未继承 IDisposable。以下是 FileAttachment 的反编译代码 resharper 显示:
namespace Microsoft.TeamFoundation.WorkItemTracking.Proxy
{
public struct FileAttachment
{
private Stream m_localFile;
...
public Stream LocalFile
{
get
{
return this.m_localFile;
}
set
{
this.m_localFile = value;
}
}
}
}
我们如何确认流对象是按引用还是按值复制的?如果是按值复制,我们如何才能阻止内存泄漏?
如果对象是 class
,则对象是引用类型,而 value type if it is a struct
or enumerable
. FileAttachment 是 class
。
因此,赋值 attachment.LocalFile = stream;
不会导致内存泄漏,因为它是通过引用赋值进行复制。
还应注意,attachment.LocalFile
属性 一旦退出 using()
作用域,将指向无效数据,如果有任何尝试访问,将抛出异常属性.
我按照此处的示例 (How to attach a file to work item in TFS without physical file path?) 将文件附加到 TFS 中的工作项,方法是使用流而不是物理文件。我有以下代码:
internal static void AddAttachment(WorkItemServer server, Project teamProject, string fileContent, WorkItem workItem)
{
FileAttachment attachment = new FileAttachment();
using (MemoryStream stream = new MemoryStream())
{
using (StreamWriter writer = new StreamWriter(stream))
{
writer.Write(fileContent);
writer.Flush();
stream.Position = 0;
attachment.LocalFile = stream;
attachment.AreaNodeUri = "";
attachment.FileNameGUID = Guid.NewGuid();
attachment.ProjectUri = teamProject.Uri.ToString();
server.UploadFile(attachment);
const string c_UpdatePackage = @"<validxml>";
XmlDocument updatePackage = new XmlDocument();
updatePackage.LoadXml(string.Format(c_UpdatePackage, workItem.Id /*work item ID*/, workItem.Rev /*work item latest revision*/, "Test attachment", attachment.FileNameGUID, DateTime.Now.ToUniversalTime().ToString("yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fff'Z'"), fileContent.Length, "John Smith", "http://localhost:8080/tfs/defaultcollection"));
XmlElement outputPackage;
string dbStamp;
IMetadataRowSets metadata;
server.Update(Guid.NewGuid().ToString(), updatePackage.DocumentElement, out outputPackage, null, out dbStamp, out metadata);
}
}
}
我的问题:作业中
attachment.LocalFile = stream;
流是通过引用还是通过值复制到 attachment.LocalFile?如果它是通过引用复制的,我认为上面的代码不会有内存泄漏,因为它正在使用中处理流:
using (MemoryStream stream = new MemoryStream()) { ... }
但是如果它按值复制(制作流的副本),这将导致内存泄漏,因为 FileAttachment 没有被释放,对吧?如果存在内存泄漏,我认为无法修复此内存泄漏,因为 FileAttachment 未继承 IDisposable。以下是 FileAttachment 的反编译代码 resharper 显示:
namespace Microsoft.TeamFoundation.WorkItemTracking.Proxy
{
public struct FileAttachment
{
private Stream m_localFile;
...
public Stream LocalFile
{
get
{
return this.m_localFile;
}
set
{
this.m_localFile = value;
}
}
}
}
我们如何确认流对象是按引用还是按值复制的?如果是按值复制,我们如何才能阻止内存泄漏?
如果对象是 class
,则对象是引用类型,而 value type if it is a struct
or enumerable
. FileAttachment 是 class
。
因此,赋值 attachment.LocalFile = stream;
不会导致内存泄漏,因为它是通过引用赋值进行复制。
还应注意,attachment.LocalFile
属性 一旦退出 using()
作用域,将指向无效数据,如果有任何尝试访问,将抛出异常属性.