The Result of a Query Cannot be Enumerated More than Once (C#) (Entity Framework) (Stored Procedure)

Question

When I get to db.GetLabelComponentsByLabelID(LabelIDs.ElementAt(i).Value.ToString()).ToList()

I get the following exception: The Result of a Query Cannot be Enumerated More than Once

I tried to change LabelComponents by calling ToList() like this answer suggested.

long? GroupID = db.GetGroupIDByName("PrintTest").SingleOrDefault();
ObjectResult<long?> LabelIDs = db.GetLabelIDSFromGroupingsByGroupID(GroupID.ToString());
for (int i = 0; i < LabelIDs.Count(); i++)
{
    var LabelComponents = db.GetLabelComponentsByLabelID(LabelIDs.ElementAt(i).Value.ToString()).ToList();
    List<Component> Label = new List<Component>();

    for(int j = 0; j < LabelComponents.Count(); j++)
    {
        ....
        ....

The code in the first sentence doesn't match your code snippet, are you sure you have `ToList` in your actual code? — DavidG, Nov 01 '17 at 14:56
@DavidG var LabelComponents = db.GetLabelComponentsByLabelID(LabelIDs.ElementAt(i).Value.ToString()).ToList(); It is there. No? — DragonMasa, Nov 01 '17 at 15:01
Put the `.ToList()` after `GetLabelIDSFromGroupingsByGroupID()` — Peter Szekeli, Nov 01 '17 at 15:02
You need `ToList` on the *first* db call, you are enumerating the `LabelIDs` value multiple times. — DavidG, Nov 01 '17 at 15:02

score 3 · Accepted Answer · answered Nov 01 '17 at 15:05

3

You need ToList on the first db call because you are enumerating the LabelIDs value multiple times. LabelIDs.Count runs the query the first time, then LabelIDs.ElementAt runs it again later on.

answered Nov 01 '17 at 15:05

DavidG

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The Result of a Query Cannot be Enumerated More than Once (C#) (Entity Framework) (Stored Procedure)

1 Answers1