Postgresql Devart EF：底层提供程序在打开时失败答案

【问题标题】：Postgresql Devart EF : The underlying provider failed on OpenPostgresql Devart EF：底层提供程序在打开时失败
【发布时间】：2018-06-05 08:21:35
【问题描述】：

在我们的 Postgre Db 上使用实体框架执行简单的读取查询时，我遇到了这个异常，在引发此异常的代码中，我不使用事务代码不会系统地失败，而是随机地失败

这是堆栈跟踪：

{
  "Depth": 0,
  "ClassName": "System.Data.Entity.Core.EntityException",
  "Message": "The underlying provider failed on Open.",
  "Source": "EntityFramework",
  "StackTraceString": "   at System.Data.Entity.Core.EntityClient.EntityConnection.Open()\r\n   at System.Data.Entity.Core.Objects.ObjectContext.EnsureConnection(Boolean shouldMonitorTransactions)\r\n   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n   at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__5()\r\n   at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)\r\n   at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()\r\n   at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()\r\n   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)\r\n  ......,
  "RemoteStackTraceString": null,
  "RemoteStackIndex": 0,
  "ExceptionMethod": {
    "Name": "Open",
    "AssemblyName": "EntityFramework",
    "AssemblyVersion": "6.0.0.0",
    "AssemblyCulture": "",
    "ClassName": "System.Data.Entity.Core.EntityClient.EntityConnection",
    "Signature": "Void Open()",
    "MemberType": 8
  },
  "HResult": -2146233087,
  "HelpURL": null
},
{
  "Depth": 1,
  "ClassName": "System.InvalidOperationException",
  "Message": "The current TransactionScope is already complete.",
  "Source": "System.Transactions",
  "StackTraceString": "   at System.Transactions.Transaction.get_Current()\r\n   at Devart.Common.DbConnectionFactory.a(DbConnectionBase A_0)\r\n   at Devart.Common.DbConnectionFactory.b(DbConnectionBase A_0)\r\n   at Devart.Common.DbConnectionClosed.Open(DbConnectionBase outerConnection)\r\n   at Devart.Common.DbConnectionBase.Open()\r\n   at Devart.Data.PostgreSql.PgSqlConnection.Open()\r\n   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext](TTarget target, Action`2 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)\r\n   at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection connection, DbInterceptionContext interceptionContext)\r\n   at System.Data.Entity.Core.EntityClient.EntityConnection.Open()",
  "RemoteStackTraceString": null,
  "RemoteStackIndex": 0,
  "ExceptionMethod": {
    "Name": "get_Current",
    "AssemblyName": "System.Transactions",
    "AssemblyVersion": "4.0.0.0",
    "AssemblyCulture": "",
    "ClassName": "System.Transactions.Transaction",
    "Signature": "System.Transactions.Transaction get_Current()",
    "MemberType": 8
  },
  "HResult": -2146233079,
  "HelpURL": null
}

在 Db 中启用事务，我设置了max_prepared_transactions = max_connections =100

我将 Devart 提供程序与 EF 一起用于 Postgresql 数据库

知道为什么/何时发生此异常吗？

【问题讨论】：

我们使用 Devart 的库，它们通常非常可靠。显然，你的情况有些不妙。您的连接字符串是什么样的？创建数据库上下文的代码是什么样的？
连接字符串是：User Id=******;Password=******;Host=myHost;Database=myDb;Persist Security Info=True;Initial Schema=myInitialSchema ;Port=5432;Unicode=True 他构造的 dbContext 是：public MyContext(string nameOrConnectionString) { .... }
1.请向我们发送一个工作项目（尽可能简单）并指定重现错误应遵循的确切步骤：devart.com/company/contactform.html。 2. 告诉我们等待错误发生的大致时间。

标签： c# postgresql transactions entity-framework-6 devart

【解决方案1】：

通过在创建事务作用域时设置 TransactionScopeAsyncFlowOption.Enabled 解决的问题

https://particular.net/blog/transactionscope-and-async-await-be-one-with-the-flow

【讨论】：