我有针对MySQL数据库运行的此方法，结果是所有代码如下所示的异常。
然后尝试使用take（10）方法查询，它可以正常工作，但还不能弄清楚原因。
我要遍历的表具有数百万行。有人可以解释发生了什么，为什么？谢谢
public IHttpActionResult retentionRate() {
DateTime today = DateTime.Today;
DateTime firstOfThisMonth = new DateTime(today.Year, today.Month, 1);
DateTime LastYearDate = DateTime.Today.AddDays(-365);
var activeInDateRange = (from mp in FitnessDbo.memberproductinfoes
where mp.mepi_expirydate >= LastYearDate &&
mp.mepi_activationdate < today
select new
{
mepi_memberproductinfoid = mp.mepi_memberproductinfoid,
mepi_memberid = mp.mepi_memberid,
mepi_activationdate = (mp.mepi_activationdate < LastYearDate ? LastYearDate : mp.mepi_activationdate),
mepi_expirydate = (mp.mepi_expirydate > today ? today : mp.mepi_expirydate),
mepi_prodtype = mp.mepi_prodtype,
mepi_producttypeinfo = mp.mepi_producttypeinfo,
mepi_memberproducttype = mp.mepi_memberproducttype,
mepi_status = mp.mepi_status
}).ToList();
return Ok(activeInDateRange);
}
使用Take（）方法：
public IHttpActionResult retentionRate() {
DateTime today = DateTime.Today;
DateTime firstOfThisMonth = new DateTime(today.Year, today.Month, 1);
DateTime LastYearDate = DateTime.Today.AddDays(-365);
var activeInDateRange = (from mp in FitnessDbo.memberproductinfoes
where mp.mepi_expirydate >= LastYearDate &&
mp.mepi_activationdate < today
select new
{
mepi_memberproductinfoid = mp.mepi_memberproductinfoid,
mepi_memberid = mp.mepi_memberid,
mepi_activationdate = (mp.mepi_activationdate < LastYearDate ? LastYearDate : mp.mepi_activationdate),
mepi_expirydate = (mp.mepi_expirydate.Value > today? today : mp.mepi_expirydate),
mepi_prodtype = mp.mepi_prodtype,
mepi_producttypeinfo = mp.mepi_producttypeinfo,
mepi_memberproducttype = mp.mepi_memberproducttype,
mepi_status = mp.mepi_status
}).Take(10);
}
我收到的异常
{"message":"An error has occurred.",
"exceptionMessage":"Calling 'Read' when the data reader is closed is not a valid operation.",
"exceptionType":"System.Data.Entity.Core.EntityCommandExecutionException",
"stackTrace":
" at System.Data.Entity.Core.Common.Internal.Materialization.Shaper\`1.HandleReaderException(Exception e)\r\n
at System.Data.Entity.Core.Common.Internal.Materialization.Shaper\`1.StoreRead()\r\n at System.Data.Entity.Core.Common.Internal.Materialization.Shaper\`1.SimpleEnumerator.MoveNext()\r\n
at System.Data.Entity.Internal.LazyEnumerator\`1.MoveNext()\r\n
at System.Collections.Generic.List\`1..ctor(IEnumerable\`1 collection)\r\n
at System.Linq.Enumerable.ToList[TSource](IEnumerable\`1 source)\r\n
at BI_leejam.Controllers.MembersController.retentionRate() in C:\\Users\\ahijazi\\source\\repos\\BI_leejam\\BI_leejam\\Controllers\\MembersController.cs:line 123\r\n
at lambda_method(Closure , Object , Object[] )\r\n
at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass6_2.<GetExecutor>b__2(Object instance, Object[] methodParameters)\r\n
at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)\r\n
at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary\`2 arguments, CancellationToken cancellationToken)\r\n
--- End of stack trace from previous location where exception was thrown ---\r\n
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n
at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__1.MoveNext()\r\n
--- End of stack trace from previous location where exception was thrown ---\r\n
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n
at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__5.MoveNext()\r\n
--- End of stack trace from previous location where exception was thrown ---\r\n
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n
at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__15.MoveNext()",
"innerException":{"message":"An error has occurred.",
"exceptionMessage":"Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.",
"exceptionType":"MySql.Data.MySqlClient.MySqlException",
"stackTrace":
" at MySql.Data.MySqlClient.Interceptors.ExceptionInterceptor.Throw(Exception exception)\r\n
at MySql.Data.MySqlClient.MySqlConnection.Throw(Exception ex)\r\n at MySql.Data.MySqlClient.MySqlConnection.HandleTimeoutOrThreadAbort(Exception ex)\r\n
at MySql.Data.MySqlClient.MySqlDataReader.Read()\r\n
at MySql.Data.EntityFramework.EFMySqlDataReader.Read()\r\n
at System.Data.Entity.Core.Common.Internal.Materialization.Shaper\`1.StoreRead()",
"innerException":{"message":"An error has occurred.",
"exceptionMessage":"Timeout in IO operation",
"exceptionType":"System.TimeoutException",
"stackTrace":
" at MySql.Data.MySqlClient.TimedStream.StopTimer()\r\n
at MySql.Data.MySqlClient.TimedStream.Read(Byte[] buffer, Int32 offset, Int32 count)\r\n
at MySql.Data.MySqlClient.MySqlStream.ReadFully(Stream stream, Byte[] buffer, Int32 offset, Int32 count)\r\n
at MySql.Data.MySqlClient.MySqlStream.LoadPacket()\r\n
at MySql.Data.MySqlClient.MySqlStream.ReadPacket()\r\n
at MySql.Data.MySqlClient.NativeDriver.FetchDataRow(Int32 statementId, Int32 columns)\r\n
at MySql.Data.MySqlClient.Driver.FetchDataRow(Int32 statementId, Int32 columns)\r\n
at MySql.Data.MySqlClient.ResultSet.GetNextRow()\r\n
at MySql.Data.MySqlClient.ResultSet.NextRow(CommandBehavior behavior)\r\n
at MySql.Data.MySqlClient.MySqlDataReader.Read()"}}}
尝试将此添加到您的控制器：
protected override void Dispose(bool disposing)
{
if (disposing)
{
if (this.FitnessDbo != null) { this.FitnessDbo.Dispose(); }
}
base.Dispose(disposing);
}