有趣的网站代码,专业网站设计师去哪找,石狮网站建设费用,证书查询入口官网EFCore 5 中的 SavepointsIntroEFCore 5中引入了一个新特性#xff0c;叫做 Savepoints#xff0c;主要是事务中使用#xff0c;个人感觉有点类似于 Windows 上的系统还原点#xff0c;如果事务发生了异常#xff0c;可以回滚到某一个还原点。Savepoints当我们在一个事务里… EFCore 5 中的 SavepointsIntroEFCore 5中引入了一个新特性叫做 Savepoints主要是事务中使用个人感觉有点类似于 Windows 上的系统还原点如果事务发生了异常可以回滚到某一个还原点。Savepoints当我们在一个事务里执行 SaveChanges 的时候EF Core 会在保存数据之前自动的创建一个 savepointSavepoints 有点类似于系统还原点的概念我们可以回滚到指定的 savepoint,当事务发生错误的时候会自动回滚到事务创建的 savepoint 回滚到事务开始之前的状态以便于我们做重试或可能的修复错误或其他逻辑。我们可以通过 CreateSavepoint 来手动创建一个 savepoint使用 RollbackToSavepoint 来回滚到某一个 savepoint来看一个微软的示例代码吧using var context new BloggingContext();
using var transaction context.Database.BeginTransaction();try
{context.Blogs.Add(new Blog { Url https://devblogs.microsoft.com/dotnet/ });context.SaveChanges();transaction.CreateSavepoint(BeforeMoreBlogs);context.Blogs.Add(new Blog { Url https://devblogs.microsoft.com/visualstudio/ });context.Blogs.Add(new Blog { Url https://devblogs.microsoft.com/aspnet/ });context.SaveChanges();transaction.Commit();
}
catch (Exception)
{// If a failure occurred, we rollback to the savepoint and can continue the transactiontransaction.RollbackToSavepoint(BeforeMoreBlogs);// TODO: Handle failure, possibly retry inserting blogs
}
Sample我们自己来动手一试示例代码如下var services new ServiceCollection();
services.AddDbContextTestDbContext(options
{options.UseSqlite(Data SourceApplication.db;CacheShared).LogTo(Console.WriteLine, LogLevel.Warning);
});
using var provider services.BuildServiceProvider();
using var scope provider.CreateScope();
var dbContext scope.ServiceProvider.GetRequiredServiceTestDbContext();
dbContext.Database.EnsureCreated();
Console.WriteLine($Posts count:{dbContext.Posts.Count()});
using var transaction dbContext.Database.BeginTransaction();
try
{dbContext.Posts.Add(new Post() { Author Tom, Title Date changed, PostedAt DateTime.UtcNow, });dbContext.Posts.Add(new Post() { Author Tom, Title Date changed, PostedAt DateTime.UtcNow, });dbContext.SaveChanges();transaction.CreateSavepoint(Stage1);Console.WriteLine($Posts count:{dbContext.Posts.Count()});dbContext.Posts.Add(new Post() { Author Alice, Title Test, PostedAt DateTime.UtcNow, });dbContext.SaveChanges();transaction.CreateSavepoint(Stage2);Console.WriteLine($Posts count:{dbContext.Posts.Count()});throw new InvalidOperationException();transaction.Commit();
}
catch (Exception)
{Console.WriteLine(Exception throw);transaction.RollbackToSavepoint(Stage1);
}Console.WriteLine($Posts count:{dbContext.Posts.Count()});
示例代码中创建了两个 savepoint然后抛出了一个异常捕获异常后回滚到第一个 savepoint输出结果如下output可以看到只有第一个 savepoint 之前的数据保存了下来第二个 savepoint 虽然数据成功保存了但是又被回滚了最终只有第一个 savepoint 之前的数据变更被保存了下来More通过 savepoint 我们就可以使得事务控制更加精细可以更能够好的控制事务中的数据变更但是需要注意的是这个功能不要和 Sql Server 中的 Multiple Active Result Sets 一起使用一旦发生了错误事务控制可能会发生不可预期的情况。Savepoints are incompatible with SQL Servers Multiple Active Result Sets, and are not used. If an error occurs during SaveChanges, the transaction may be left in an unknown state.Referenceshttps://docs.microsoft.com/en-us/ef/core/saving/transactions#savepointshttps://github.com/WeihanLi/SamplesInPractice/blob/master/EF5Samples/SavePointsTest.cs
