Der Versuch, DataReader zu schließen

Question

Der Versuch, die Datenbank mit der folgenden Funktion zu aktualisieren. Aber immer, wenn ich versuche, diese Funktion auszuführen, heißt es, dass ich meinen DataReader nicht geschlossen habe. Fehler - Mit diesem Befehl ist bereits ein offener DataReader verbunden, der zuerst geschlossen werden muss. Willst du fragen, wo ich es schließe? Vielen Dank.

private static void updateICAT(DataSet s) 
    { 
     DataTable excelTable = s.Tables[7]; 
     DataTable contacts = getXML(); 

     Context _db = new Context(); 
     var updateICAT = _db.ICATs; 

     int counter = 1; 

     foreach(ICAT icat in updateICAT) 
     { 

      if(icat.ICATName != "--NOT AVAILABLE--") 
      { 
       DataRow r = contacts.Select("ICATName='" + excelTable.Rows[counter].ItemArray[2].ToString().Trim() + "'")[0]; 
       if (icat.ICATName != excelTable.Rows[counter].ItemArray[0].ToString()) 
       { 

        System.Diagnostics.Debug.WriteLine("not match"); 
        System.Diagnostics.Debug.WriteLine("current Icat id " + icat.ICATID + " current counter " + counter); 
        var updateCurrentICAT = updateICAT.SingleOrDefault(p => p.ICATID == counter); 
        updateCurrentICAT.ICATName = excelTable.Rows[counter].ItemArray[0].ToString().Trim(); 
        updateCurrentICAT.MEGroup = excelTable.Rows[counter].ItemArray[1].ToString().Trim(); 
        updateCurrentICAT.EscalationDisplayName = excelTable.Rows[counter].ItemArray[2].ToString().Trim(); 
        updateCurrentICAT.EscalationUserName = r["Username"].ToString().Trim(); 
        updateCurrentICAT.EscalationMail = r["Mail"].ToString().Trim(); 
       } 
      } 
      counter++; 
     } 
    } 

Der Fehler ist auf

var updateCurrentICAT = updateICAT.SingleOrDefault(p => p.ICATID == counter); 

Unterhalb der Trace-Stack ist:

[InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.] 
    System.Data.SqlClient.SqlInternalConnectionTds.ValidateConnectionForExecute(SqlCommand command) +1543253 
    System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute(String method, SqlCommand command) +101 
    System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async) +268 
    System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite) +91 
    System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) +53 
    System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) +161 
    System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior) +41 
    System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior) +12 
    System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.<Reader>b__c(DbCommand t, DbCommandInterceptionContext`1 c) +14 
    System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch(TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed) +72 
    System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.Reader(DbCommand command, DbCommandInterceptionContext interceptionContext) +402 
    System.Data.Entity.Internal.InterceptableDbCommand.ExecuteDbDataReader(CommandBehavior behavior) +166 
    System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior) +12 
    System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +36 

[EntityCommandExecutionException: An error occurred while executing the command definition. See the inner exception for details.] 
    System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +103 
    System.Data.Entity.Core.Objects.Internal.ObjectQueryExecutionPlan.Execute(ObjectContext context, ObjectParameterCollection parameterValues) +758 
    System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__6() +90 
    System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction(Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess) +288 
    System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__5() +154 
    System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Func`1 operation) +190 
    System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +283 
    System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0() +15 
    System.Data.Entity.Internal.LazyEnumerator`1.MoveNext() +45 
    System.Linq.Enumerable.SingleOrDefault(IEnumerable`1 source) +121 
    System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__2(IEnumerable`1 sequence) +40 
    System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.ExecuteSingle(IEnumerable`1 query, Expression queryRoot) +59 
    System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression) +114 
    System.Data.Entity.Internal.Linq.DbQueryProvider.Execute(Expression expression) +116 
    System.Linq.Queryable.SingleOrDefault(IQueryable`1 source, Expression`1 predicate) +249 
    WITS_v4.Pages.updateRecord.updateICAT(DataSet s) in C:\Users\khongkok\Source\Repos\WITS\WITS v4\Pages\updateRecord.aspx.cs:94 
    WITS_v4.Pages.updateRecord.Page_Load(Object sender, EventArgs e) in C:\Users\khongkok\Source\Repos\WITS\WITS v4\Pages\updateRecord.aspx.cs:22 
    System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +51 
    System.Web.UI.Control.OnLoad(EventArgs e) +95 
    System.Web.UI.Control.LoadRecursive() +59 
    System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2952 

Answer 1

ich die Verwendung des updateICAT.SingleOrDefault in der LINQ IEnumerable foreach-Schleife denken verursacht das Problem. Eine Möglichkeit, dies zu lösen, besteht darin, eine zweite Context zu verwenden und db2.ICATs.SingleOrDefault innerhalb der Schleife aufzurufen, wie unten gezeigt.

private static void updateICAT(DataSet s) 
{ 
    DataTable excelTable = s.Tables[7]; 
    DataTable contacts = getXML(); 

    Context _db = new Context(); 
    Context db2 = new Context(); 
    var updateICAT = _db.ICATs; 

    int counter = 1; 

    foreach(ICAT icat in updateICAT) 
    { 

     if(icat.ICATName != "--NOT AVAILABLE--") 
     { 
      DataRow r = contacts.Select("ICATName='" + excelTable.Rows[counter].ItemArray[2].ToString().Trim() + "'")[0]; 
      if (icat.ICATName != excelTable.Rows[counter].ItemArray[0].ToString()) 
      { 

       System.Diagnostics.Debug.WriteLine("not match"); 
       System.Diagnostics.Debug.WriteLine("current Icat id " + icat.ICATID + " current counter " + counter); 
       var updateCurrentICAT = db2.ICATs.SingleOrDefault(p => p.ICATID == counter); 
       updateCurrentICAT.ICATName = excelTable.Rows[counter].ItemArray[0].ToString().Trim(); 
       updateCurrentICAT.MEGroup = excelTable.Rows[counter].ItemArray[1].ToString().Trim(); 
       updateCurrentICAT.EscalationDisplayName = excelTable.Rows[counter].ItemArray[2].ToString().Trim(); 
       updateCurrentICAT.EscalationUserName = r["Username"].ToString().Trim(); 
       updateCurrentICAT.EscalationMail = r["Mail"].ToString().Trim(); 
      } 
     } 
     counter++; 
    } 
}