查询的结果不能被枚举多次（C#）（实体框架）（存储过程）

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++)
    {
        ....
        ....

Answer 1

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.