CODEWITHSUNDEEP
linq-to-entities
Bob Cummings
Bob Cummings

Reputation: 422

check for empty results from linq to data entites query

I have been looking everywhere and can not seem to solve this. I have the following linq to data entities that sometime returns an empty set. But I can not seem to test for the empty set?

           IEnumerable<string> xrefLineItems = from xref in db.wysLkupItemCrossRefs
                                            where xref.EndPointCustID == inCustID
                                            select xref.BuyersItemNo;

Everytime I try this it evaluates to false whether or not there are entries in the Result set?

        if (xrefLineItems == Enumerable.Empty<string>())
        {  }

If I try to use xrefLineItems.Any() I get the follow exception

The method 'First' can only be used as a final query operation. Consider using the method 'FirstOrDefault' in this instance instead.

cheers bob

Here is the stack trace

Line 146:            
Line 147:            bool isEmpty;
Line 148:            if (xrefLineItems.Any())
Line 149:            {
Line 150:                isEmpty = true;


Source File: H:\DirectEDI\MVC_EDI\MVC_EDI\MVC_EDI\Controllers\DirectEDIController.cs    Line: 148

Stack Trace:

[NotSupportedException: The method 'First' can only be used as a final query operation. Consider using the method 'FirstOrDefault' in this instance instead.]
   System.Data.Objects.ELinq.FirstTranslator.TranslateUnary(ExpressionConverter parent, DbExpression operand, MethodCallExpression call) +100
   System.Data.Objects.ELinq.UnarySequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) +81
   System.Data.Objects.ELinq.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod) +14
   System.Data.Objects.ELinq.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) +102
   System.Data.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +54
   System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +110
   System.Data.Objects.ELinq.EqualsTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq) +70
   System.Data.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +54
   System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +110
   System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input) +80
   System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding) +88
   System.Data.Objects.ELinq.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda) +85
   System.Data.Objects.ELinq.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) +37
   System.Data.Objects.ELinq.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod) +14
   System.Data.Objects.ELinq.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) +102
   System.Data.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +54
   System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +110
   System.Data.Objects.ELinq.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda) +49
   System.Data.Objects.ELinq.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) +37
   System.Data.Objects.ELinq.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod) +14
   System.Data.Objects.ELinq.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) +102
   System.Data.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +54
   System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +110
   System.Data.Objects.ELinq.ExpressionConverter.Convert() +16
   System.Data.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption) +110
   System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +149
      System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() +44
   System.Linq.Enumerable.Any(IEnumerable`1 source) +71
   MVC_EDI.Controllers.DirectEDIController.hasTrakNumber(Guid inOrderID) in H:\DirectEDI\MVC_EDI\MVC_EDI\MVC_EDI\Controllers\DirectEDIController.cs:148

Upvotes: 3

Views: 2916

Answers (2)

Craig Stuntz
Craig Stuntz

Reputation: 126547

Any() is the correct method.

Neither Any() nor Count() call First(). If you are seeing this, then your bug is elsewhere. Look at the call stack for the exception.

Upvotes: 2

Filipe Pinheiro
Filipe Pinheiro

Reputation: 1102

you can use Count

IEnumerable<string> xrefLineItems = from xref in db.wysLkupItemCrossRefs
                                    where xref.EndPointCustID == inCustID
                                    select xref.BuyersItemNo;  

if (xrefLineItems.Count() == 0)
{
  // empty
}

Upvotes: 0

Related Questions