Is it possible to map IQueryable to IQueryable?

问题

This is a question for Automapper professionals. I have tried to do query mapping for several days already - and no luck. Seems like Automapper is not intended to be used the way I want to use it. But maybe I am wrong. So here is the question...

I have such classes:

CatDto (Name, Age, Toys (collection of ToyDto objects))
ToyDto (CatName, ToyName, Cat (parent CatDto object))
Cat (comes from Entity Framework, has properties similar to those in CatDto)
Toy (comes from Entity Framework, has properties similar to those in ToyDto)

I want to write a generic read function in my data access layer, something like this:

IEnumerable<CatDto> Read(IQueryable<CatDto> query) {
    // here "query" is converted 
    // to Entity Framework query by means of AutoMapper,
    // EF query gets executed,
    // I convert EF entities (Cat) back to CatDto - this is not essential
    // result is returned
}

I will call this function in different manners. Example:

var q = new ObjectModel.Collection(Of CatDto)).AsQueryable();
q = q.Where(c => c.Toys.Count() > 1);
var someResultVar = Read(q);

So far any attempts to implement such behavior have failed. I wonder if Automapper is a helper here or am I going completely wrong way?

回答1:

I believe the functionality you want is in UseAsDataSource

You can't map IQueryable, but you shouldn't need to with UseAsDataSource Example

IQueryable<CatDto> someResultVar  = new ObjectModel.Collection(Of CatDto)).AsQueryable().UseAsDataSource().For(Of OrderLineDTO).Where(c => c.Toys.Count() > 1);

When you enumerate it will convert Lambda from CatDto to CatEf and call ProjectTo<CatDto> and return CatDto objects

来源：https://stackoverflow.com/questions/37965593/is-it-possible-to-map-iqueryablecatdto-to-iqueryablecatef

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