在实体框架中将LINQ动态查询转换为IQueryable

Question

I am trying to convert a LINQ query that joins two tables to IQueryable type in Entity Framework so I can further apply filter expression on it.

Here's the code:

IQueryable<Bill_Joined_V1> bills = 
     (from primary in _billEntity.BillTable
      join secondary in _billEntity.BillInfoTable on primary.BillID equals secondary.BillID
      orderby primary.BillID
      select new
                {
                    primary.BillID,
                    primary.CustomerID,
                    secondary.Name,
                    secondary.Value
                }).AsQueryable<Bill_Joined_V1>().Where(FilterExp);

The entity classes are as follows:

public class Bill_V1
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid BillID { get; set; }

    public string BillTypeID { get; set; }
    public Guid CustomerID { get; set; }
    public Guid UserID { get; set; }

    [ForeignKey("UserID")]
    public virtual User_V1 UserTable { get; set; }

    public double AmountDue { get; set; }
}

public class BillInfo_V1
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long BillInfoID { get; set; }

    public Guid BillID { get; set; }

    [ForeignKey("BillID")]
    public virtual Bill_V1 BillTable { get; set; }

    public string Name { get; set; }
    public string Value { get; set; }
}

// Dummy bill record for query purpose
public class Bill_Joined_V1
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long BillRecID { get; set; }

    public Guid BillID { get; set; }
    [ForeignKey("BillID")]
    public virtual Bill_V1 BillTable { get; set; }

    public Guid CustomerID { get; set; }
    [ForeignKey("CustomerID")]
    public virtual Customer_V1 CustomerTable { get; set; }

    public string Name { get; set; }
    public string Value { get; set; }

}

The code does not compile. It produces error message saying

'System.Linq.IQueryable' does not contain a definition for 'AsQueryable' and the best extension method overload 'System.Linq.Queryable.AsQueryable(System.Collections.Generic.IEnumerable)' has some invalid arguments

Is there a way to convert the LINQ query to IQueryable type without putting the query result to a physical table? How do I work around this? Thanks.

Answer 1

You shouldn't need to call .AsQueryable() . .Where() is designed to return an IQueryable of appropriate type. But the exact type of IQueryable in your code won't be IQueryable<Bill_Joined_V1> because you are using an anonymous type. What you really need to do is not use an anonymous type here:

select new
                                {
                                    primary.BillID,
                                    primary.CustomerID,
                                    secondary.Name,
                                    secondary.Value
                                }).

Instead, do

select new Bill_Joined_V1 { /* initialize properties */ }