在服务中打开和关闭多个连接时出现 SAP Sybase SQL Anywhere NullReference 异常

问：

目前，我遇到了一个问题，即SAP Sybase SQL Anywhere随机抛出一个执行大量sql查询的服务。连接总是在一个块中创建，并正确打开和关闭。并行连接不多，但一段时间后（随机）打开和关闭连接时会引发以下异常：NullReferenceExceptionusing

Exception: System.NullReferenceException: The object was not set to an instance.
   bei iAnywhere.Data.SQLAnywhere.SAConnection.Dispose(Boolean disposing)
   bei iAnywhere.Data.SQLAnywhere.SAConnection.Close()
   bei iAnywhere.Data.SQLAnywhere.SAConnection.get_State()
   bei product.Framework.DAL.ConnectionManager.GetOpenPoolConnection[T](String ModuleName, String Connection, Boolean resizePoolOnRimteOut, Int64 Time
Out, Boolean isSecondTry)
   bei product.Framework.DAL.ORM.Sybase.SybaseStack.LoadDataFromDB[T](String where_part, String connectionStringName, Object[] sa_params)
   bei product.Framework.DAL.ORM.Sybase.SybaseStack.LoadData[T](String optWherePart, Object[] parameter)
   bei product.PlugIn.DocCenterClient.AS_Modules.DefaultInstanceDataExportModule.DoSingalProcessing()
   bei System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCt
x)
   bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   bei System.Threading.ThreadHelper.ThreadStart()

有人知道是什么导致了这种行为吗？我们无法弄清楚它背后的任何规律性。

抛出异常，这将创建一个新的并打开它：GetOpenPoolConnectionSAConnection

internal static T GetOpenPoolConnection<T>(string Connection = "Default") where T : DbConnection
{
    // Read connection string from static dictionary
    string cConnectionString = GetConnectionString(Connection);
    T cToReturn = null;

    if (cConnectionString != null)
    {
        if (typeof(T) == typeof(SqlConnection))
        {
            cToReturn = (new SqlConnection(cConnectionString) as T);
            cToReturn.Open();
        }
        else if (typeof(T) == typeof(SAConnection))
        {
            cToReturn = (new SAConnection(cConnectionString) as T);
            cToReturn.Open();
        }
        else if (typeof(T) == typeof(OdbcConnection))
        {
            cToReturn = (new OdbcConnection(cConnectionString) as T);
            cToReturn.Open();
        }

        return cToReturn;
    }
    else
    {
        return null;
    }
}

此函数称为：

using (SAConnection connection = DAL.ConnectionManager.GetOpenPoolConnection<SAConnection>())
{
    var res = connection.Query<Guid>("SELECT InstanceDataGuid FROM AS_EX_Objects WHERE ExchangeObjectId = ?", new { ExchangeObjectId = ic.ItemId.ToString() });
    if (res.Any())
    {
        instanceDataGuid = res.Single<Guid>();
   }
}

我们使用 SAP SQL Anywhere 12 作为数据库引擎/服务器，使用 SAP SQL Anywhere 16 作为客户端组件。项目和数据库驱动程序仅为 64 位。导致此问题的所有 bug 都应在我们使用的 ADO .Net 驱动程序版本中修复（在 bug 修复中，请参阅工程案例 #797124、#741721 和 #738144）。