Trying to close DataReader

Question

Trying to update the database with the function below. But then whenever i trying to run this function, it stated that I didn't closed my DataReader. error - There is already an open DataReader associated with this Command which must be closed first. Want to ask where do I close it. Thank you.

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++;
        }
    }

The error is on

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

Below is the stack trace:

    [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

I'm thinking the use of the updateICAT.SingleOrDefault inside the LINQ IEnumerable foreach loop is causing the problem. One way you might solve this is by converting to using a second Context and calling db2.ICATs.SingleOrDefault inside the loop as shown below.

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++;
    }
}