Question

以下代码抛出InvalidOperationException：Sequence包含多个元素。无论我是否包含Include语句，都会发生错误。

long[] customerIDs; //Method parameter. Has valid values


var results = from x in DB.CycleCounts
              //.Include(y => y.CustomerInventoryItem)
              select x;

if (customerIDs != null && customerIDs.Length > 0)
{
    results = from x in results
              where customerIDs.Contains(x.CustomerInventoryItem.CustomerID)
              select x;

}

var cycleCounts = await results.ToListAsync(); //throws InvalidOperationException

我正在使用ASP5 RC1（Core）和Entity Framework 7

Answer 1

我不确定如何看待你的模型，但我认为它们看起来像下面的东西（CycleCounts和CustomerInventoryItems之间的关系像我期望的那样多对一）：

<强>型号：

[Table("CustomerInventorys")]
public class CustomerInventory
{
    public long ID { get; set; }
    public long CustomerID { get; set; }

    public virtual ICollection<CycleCount> CycleCounts { get; set; }
}

[Table("CycleCounts")]
public class CycleCount
{
    public long ID { get; set; }

    public long CustomerInventoryItemID { get; set; }
    public virtual CustomerInventory CustomerInventoryItem  { get; set; }
}

所以如果我的建议是正确的，我建议你改写这样的代码：

    IQueryable<CycleCount> results = null;

    if (customerIDs != null && customerIDs.Length > 0)
    {
        results = from invent in DB.CustomerInventorys
                  where customerIDs.Contains(invent.CustomerID)
                  join cycle in DB.CycleCounts on invent.ID equals cycle.CustomerInventoryItemID                          
                  select cycle;    
    }
    else
        results = DB.CycleCounts;

    var cycleCounts = await results.ToListAsync();

在LINQ查询中使用Contains时，Sequence包含多个元素

1 个答案: