我希望设置一些非常类似于事务范围的东西，它在服务上创建一个版本，并在范围的末尾删除/提交。在事务范围内运行的每个SQL语句在内部查看某个连接池/事务存储，以确定它是否在范围内并做出适当的反应。呼叫者不需要将事务传递给每个呼叫。我正在寻找这个功能。
这是基本的一次性课程：
public sealed class VersionScope : IDisposable
{
private readonly GeodatabaseVersion _version;
private readonly VersionManager _versionManager;
public VersionScope(Configuration config)
{
_versionManager = new VersionManager(config);
_version = _versionManager.GenerateTempVersion();
_versionManager.Create(_version);
_versionManager.VerifyValidVersion(_version);
_versionManager.ServiceReconcilePull();
_versionManager.ReconcilePull(_version);
}
public void Dispose()
{
_versionManager.Delete(_version);
}
public void Complete()
{
_versionManager.ReconcilePush(_version);
}
}
我希望我迄今为止编写的所有代码的能力都没有任何版本的概念。我只想包括一个简单的
Version = GetCurrentVersionWithinScope()
在代码的最低级别。
如果内存中有多个实例同时运行，那么实现类似这样的事情的最安全的方法是什么，几乎没有使用错误版本的风险。
如果有一个进程正在运行的内存块的唯一标识符，我会发现我非常天真的方法。然后将当前工作版本存储到全局数组或并发字典中。然后在我需要当前版本的代码中，我使用其内存标识符块并将其映射到创建的版本。
编辑：
用法示例：
using (var scope = new VersionScope(_config))
{
AddFeature(); // This has no concept of scope passed to it, and could error out forcing a dispose() without a complete()
scope.Complete();
}
最直接的方法是使用ThreadStatic或ThreadLocal将当前版本存储在线程本地存储中。这样多线程就不会相互干扰。例如，假设我们的版本类：
public class Version {
public Version(int number) {
Number = number;
}
public int Number { get; }
public override string ToString() {
return "Version " + Number;
}
}
那么VersionScope的实现可以这样：
public sealed class VersionScope : IDisposable {
private bool _isCompleted;
private bool _isDisposed;
// note ThreadStatic attribute
[ThreadStatic] private static Version _currentVersion;
public static Version CurrentVersion => _currentVersion;
public VersionScope(int version) {
_currentVersion = new Version(version);
}
public void Dispose() {
if (_isCompleted || _isDisposed)
return;
var v = _currentVersion;
if (v != null) {
DeleteVersion(v);
}
_currentVersion = null;
_isDisposed = true;
}
public void Complete() {
if (_isCompleted || _isDisposed)
return;
var v = _currentVersion;
if (v != null) {
PushVersion(v);
}
_currentVersion = null;
_isCompleted = true;
}
private void DeleteVersion(Version version) {
Console.WriteLine($"Version {version} deleted");
}
private void PushVersion(Version version) {
Console.WriteLine($"Version {version} pushed");
}
}
它可以工作，但它不支持嵌套的范围，这是不好的，所以要修复我们需要在启动新范围时存储以前的范围，并在Complete或Dispose上恢复它：
public sealed class VersionScope : IDisposable {
private bool _isCompleted;
private bool _isDisposed;
private static readonly ThreadLocal<VersionChain> _versions = new ThreadLocal<VersionChain>();
public static Version CurrentVersion => _versions.Value?.Current;
public VersionScope(int version) {
var cur = _versions.Value;
// remember previous versions if any
_versions.Value = new VersionChain(new Version(version), cur);
}
public void Dispose() {
if (_isCompleted || _isDisposed)
return;
var cur = _versions.Value;
if (cur != null) {
DeleteVersion(cur.Current);
// restore previous
_versions.Value = cur.Previous;
}
_isDisposed = true;
}
public void Complete() {
if (_isCompleted || _isDisposed)
return;
var cur = _versions.Value;
if (cur != null) {
PushVersion(cur.Current);
// restore previous
_versions.Value = cur.Previous;
}
_isCompleted = true;
}
private void DeleteVersion(Version version) {
Console.WriteLine($"Version {version} deleted");
}
private void PushVersion(Version version) {
Console.WriteLine($"Version {version} pushed");
}
// just a class to store previous versions
private class VersionChain {
public VersionChain(Version current, VersionChain previous) {
Current = current;
Previous = previous;
}
public Version Current { get; }
public VersionChain Previous { get; }
}
}
这已经是你可以使用的东西了。示例用法（我使用单线程，但如果有多个线程单独执行此操作 - 它们不会相互干扰）：
static void Main(string[] args) {
PrintCurrentVersion(); // no version
using (var s1 = new VersionScope(1)) {
PrintCurrentVersion(); // version 1
s1.Complete();
PrintCurrentVersion(); // no version, 1 is already completed
using (var s2 = new VersionScope(2)) {
using (var s3 = new VersionScope(3)) {
PrintCurrentVersion(); // version 3
} // version 3 deleted
PrintCurrentVersion(); // back to version 2
s2.Complete();
}
PrintCurrentVersion(); // no version, all completed or deleted
}
Console.ReadKey();
}
private static void PrintCurrentVersion() {
Console.WriteLine("Current version: " + VersionScope.CurrentVersion);
}
但是，当您使用异步调用时，这将不起作用，因为ThreadLocal绑定到一个线程，但异步方法可以跨越多个线程。但是，有类似的构造名为AsyncLocal，该值将通过异步调用流动。所以我们可以在VersionScope中添加构造函数参数，指示我们是否需要异步流。事务范围以类似的方式工作 - 有TransactionScopeAsyncFlowOption传入TransactionScope构造函数，指示它是否将流经异步调用。
修改后的版本如下所示：
public sealed class VersionScope : IDisposable {
private bool _isCompleted;
private bool _isDisposed;
private readonly bool _asyncFlow;
// thread local versions
private static readonly ThreadLocal<VersionChain> _tlVersions = new ThreadLocal<VersionChain>();
// async local versions
private static readonly AsyncLocal<VersionChain> _alVersions = new AsyncLocal<VersionChain>();
// to get current version, first check async local storage, then thread local
public static Version CurrentVersion => _alVersions.Value?.Current ?? _tlVersions.Value?.Current;
// helper method
private VersionChain CurrentVersionChain => _asyncFlow ? _alVersions.Value : _tlVersions.Value;
public VersionScope(int version, bool asyncFlow = false) {
_asyncFlow = asyncFlow;
var cur = CurrentVersionChain;
// remember previous versions if any
if (asyncFlow) {
_alVersions.Value = new VersionChain(new Version(version), cur);
}
else {
_tlVersions.Value = new VersionChain(new Version(version), cur);
}
}
public void Dispose() {
if (_isCompleted || _isDisposed)
return;
var cur = CurrentVersionChain;
if (cur != null) {
DeleteVersion(cur.Current);
// restore previous
if (_asyncFlow) {
_alVersions.Value = cur.Previous;
}
else {
_tlVersions.Value = cur.Previous;
}
}
_isDisposed = true;
}
public void Complete() {
if (_isCompleted || _isDisposed)
return;
var cur = CurrentVersionChain;
if (cur != null) {
PushVersion(cur.Current);
// restore previous
if (_asyncFlow) {
_alVersions.Value = cur.Previous;
}
else {
_tlVersions.Value = cur.Previous;
}
}
_isCompleted = true;
}
private void DeleteVersion(Version version) {
Console.WriteLine($"Version {version} deleted");
}
private void PushVersion(Version version) {
Console.WriteLine($"Version {version} pushed");
}
// just a class to store previous versions
private class VersionChain {
public VersionChain(Version current, VersionChain previous) {
Current = current;
Previous = previous;
}
public Version Current { get; }
public VersionChain Previous { get; }
}
}
使用异步流的范围的示例用法：
static void Main(string[] args) {
Test();
Console.ReadKey();
}
static async void Test() {
PrintCurrentVersion(); // no version
using (var s1 = new VersionScope(1, asyncFlow: true)) {
await Task.Delay(100);
PrintCurrentVersion(); // version 1
await Task.Delay(100);
s1.Complete();
await Task.Delay(100);
PrintCurrentVersion(); // no version, 1 is already completed
using (var s2 = new VersionScope(2, asyncFlow: true)) {
using (var s3 = new VersionScope(3, asyncFlow: true)) {
PrintCurrentVersion(); // version 3
} // version 3 deleted
await Task.Delay(100);
PrintCurrentVersion(); // back to version 2
s2.Complete();
}
await Task.Delay(100);
PrintCurrentVersion(); // no version, all completed or deleted
}
}
private static void PrintCurrentVersion() {
Console.WriteLine("Current version: " + VersionScope.CurrentVersion);
}
像这样使用IDisposable有点值得怀疑。 （见Is it abusive to use IDisposable and "using" as a means for getting "scoped behavior" for exception safety?）
我，我自己觉得它对某些事情很有用。这是我使用的模式：
class LevelContext
{
private int _level;
public int CurrentLevel
{
get { return _level; }
set { _level = value < 0 ? 0 : value; }
}
public ILevel NewLevel(int depth = 1)
{
return new Level(this, depth);
}
/// <summary>
/// Provides an interface that calling code can use to handle level objects.
/// </summary>
public interface ILevel : IDisposable
{
LevelContext Owner { get; }
int Depth { get; }
void Close();
}
/// <summary>
/// Private class that provides an easy way to scope levels by allowing
/// them to participate in the "using" construct. Creation of a Level results in an
/// increase in owner's level, while disposal returns owner's level to what it was before.
/// </summary>
class Level : ILevel
{
public Level(LevelContext owner, int depth)
{
Owner = owner;
Depth = depth;
PreviousLevel = owner.CurrentLevel;
Owner.CurrentLevel += Depth;
}
public LevelContext Owner { get; private set; }
public int Depth { get; private set; }
public int PreviousLevel { get; private set; }
public void Close()
{
if (Owner != null)
{
Owner.CurrentLevel = PreviousLevel;
Owner = null;
}
}
void IDisposable.Dispose()
{
Close();
}
}
然后调用代码如下所示：
static void Main(string[] args)
{
var lc = new LevelContext();
Console.WriteLine(lc.CurrentLevel);
using (lc.NewLevel())
Console.WriteLine(lc.CurrentLevel);
Console.WriteLine(lc.CurrentLevel);
}
所以在你的情况下，你是对的 - 你需要创建跟踪当前版本的东西。在创建和处理VersionScope时，应该更新某些内容。