return LINQ Query result in IList and read it another class [duplicate]

问题

I am using ASP.NET mvc 5. I have one class that holds all the LINQ which can access to another class. now i convert the LINQ query to list variable Query and returning as IList... the i create object of this class--> call the method and get result.

now i can see in debugging object names but i can't see in foreach loop. my list hold mix data types, plus result is merging from different tables...

  public IList GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID) 
    {

        using (var db = new QualificationContext())
        {
           var Query = from a in db.FeeScheme
                        join b in db.FeeZoneSchema.Where(c => c.FeeSchemeID == 1) on a.FeeSchemeID equals b.FeeSchemeID
                        join c in db.FeeZone on b.FeeZoneID equals c.FeeZoneID
                        select new
                        {
                            FeeScheme = a.FeeSchemeID,
                            FeeZone = b.FeeZoneID,
                            FeeZone_Description = c.FeeZoneDescription
                        };

           return Query.ToList();             
        }   
    }

in controller class...

 foreach(var item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
        {
           item.???? (can't access the object here....

        }

many thanks

回答1:

You should return Generic IList of concrete (not anonymous class):

public IList<FeeSchemeModel> GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID) 
{

    using (var db = new QualificationContext())
    {
       var Query = from a in db.FeeScheme
                    join b in db.FeeZoneSchema.Where(c => c.FeeSchemeID == 1) on a.FeeSchemeID equals b.FeeSchemeID
                    join c in db.FeeZone on b.FeeZoneID equals c.FeeZoneID
                    select new FeeSchemeModel
                    {
                        FeeScheme = a.FeeSchemeID,
                        FeeZone = b.FeeZoneID,
                        FeeZone_Description = c.FeeZoneDescription
                    };

       return Query.ToList();             
    }   
}

public class FeeSchemeModel
{
    public int FeeScheme{get;set;}
    public int FeeZone{get;set;}
    public string FeeZone_Description{get;set;}
};

But I recommend to use IEnumerable<T> instead of IList<T> and use ToArray() method instead of ToList() method if you don't use special features of List<T> (such as method Add())

回答2:

IList is non-generic interface, it contains only non-generic IEnumerable definition, which enumerates objects. So type of item will be object. That's why you can see only members of System.Object class.

You should either cast item to appropriate type or use generic collection parametrized with appropriate type. But you can't use neither of these approaches while you are using anonymous objects, because you don't know anonymous type name. So, you need to create some class which you will be able to cast to:

foreach(Foo item in obj1.GetAllFeeZonesForFeeSchemeByID(1))

Or use as parameter of method return type:

public IList<Foo> GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID)

One more option is usage of dynamic type, which will resolve operations on object at runtime. You still will not be able to use IntelliSense but your code will work:

foreach(dynamic item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
{
     // use item.FeeScheme
}

来源：https://stackoverflow.com/questions/21409777/return-linq-query-result-in-ilist-and-read-it-another-class

标签

asp.net-mvc

linq

collections