C＃Web API oData筛选器失败

Question

When I define my end point API as below returning all columns, oData $filter, $Skip, $filter work fine.

 [EnableQuery]
        public IQueryable<MyList> GetMyLists()
        {
            return db.MyLists;//directly from entity table
        }

but when I select only certain columns like shown below, oData $filter, $Skip, $filter fail. Any ideas?

public IQueryable<MyResult> GetMyLists()
        {
            return db.MyLists.Select(x => new MyResult
            {
                Trade_Name = x.Trade_Name,
                price = x.price,
                remarks = x.remarks,
                Comment = x.Comment,
                GenericGroupNumber = x.GenericGroupNumber
            }); 
        }

I defined MyResult Class as:

public class MyResult
    {
        public string Trade_Name;
        public decimal? price;
        public string remarks;
        public string Comment;
        public string GenericGroupNumber;

    }

Any guidance is greatly appreciated.

Answer 1

The class MyResult has no [key] column and don't map to a table in the EDMX model. It is considered as a complex entity (like stored procedure). so you can't apply $filter, $skip.

Answer 2

oData is designed to work with the entities described in the EDMX model in the WebApiConfig.cs file, any entity outside of that will not allow you to apply $filter, $skip, etc.

You will need to define that entity in your EDMX model and place it in a controller of it's own named based on the entity name for it to work.

class MyResultsController : ApiController {
    public IQueryable<MyResult> GetMyResults()
    {
        return db.MyLists.Select(x => new MyResult
        {
            Trade_Name = x.Trade_Name,
            price = x.price,
            remarks = x.remarks,
            Comment = x.Comment,
            GenericGroupNumber = x.GenericGroupNumber
        }); 
    }
}

Then make sure you map MyResult correctly in the WebApiConfig .