public DateTime GibSomeStartDate(IEnumerable<int> partnerNumbers,DateTime startTime)
{
     var contractsStartDate = from contract in this.databaseContext.Contract
                              where partnerNumbers.Contains(contract.Pnr) 
                                 && contract.SomeDateTime >= startTime
                              select contract.SomeDateTime;
}

如果我调用contractStartDate.Min(),则会发生异常：

Unable to create a null constant value of type 'System.Collections.Generic.IEnumerable`1'. Only entity types,enumeration types or primitive types are supported in this context.

我的查询有什么问题？

> contractsStartDate属于类型
System.Data.Entity.Infrastructure.DbQuery
> EF 5.0
> databaseContext是System.Data.Entity.DbContext的子代