如果主要的想法是让SQL选择语句发送到数据库服务器只有必需的字段，而不是所有的实体字段，那么你可以这样做:

public class Class1
{
    public IList<Car> getCarsByProjectionOnSmallNumberOfProperties()
    {

        try
        {
            //Get the SQL Context:
            CompanyPossessionsDAL.POCOContext.CompanyPossessionsContext dbContext 
                = new CompanyPossessionsDAL.POCOContext.CompanyPossessionsContext();

            //Specify the Context of your main entity e.g. Car:
            var oDBQuery = dbContext.Set<Car>();

            //Project on some of its fields, so the created select statment that is
            // sent to the database server, will have only the required fields By making a new anonymouse type
            var queryProjectedOnSmallSetOfProperties 
                = from x in oDBQuery
                    select new
                    {
                        x.carNo,
                        x.eName,
                        x.aName
                    };

            //Convert the anonymouse type back to the main entity e.g. Car
            var queryConvertAnonymousToOriginal 
                = from x in queryProjectedOnSmallSetOfProperties
                    select new Car
                    {
                        carNo = x.carNo,
                        eName = x.eName,
                        aName = x.aName
                    };

            //return the IList<Car> that is wanted
            var lst = queryConvertAnonymousToOriginal.ToList();
            return lst;

        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine(ex.ToString());
            throw;
        }
    }
}

你可以这样做:

public System.Collections.IEnumerable GetDogsWithBreedNames()
{
    var db = new DogDataContext(ConnectString);
    var result = from d in db.Dogs
                 join b in db.Breeds on d.BreedId equals b.BreedId
                 select new
                        {
                            Name = d.Name,
                            BreedName = b.BreedName
                        };
    return result.ToList();
}

如果你要归还《Dogs》，你应该这样做:

public IQueryable<Dog> GetDogsWithBreedNames()
{
    var db = new DogDataContext(ConnectString);
    return from d in db.Dogs
           join b in db.Breeds on d.BreedId equals b.BreedId
           select d;
}

如果您希望Breed立即加载而不是延迟加载，只需使用适当的DataLoadOptions构造。

在c# 7中你现在可以使用元组了!这样就不需要为了返回结果而创建一个类。

下面是一个示例代码:

public List<(string Name, string BreedName)> GetDogsWithBreedNames()
{
    var db = new DogDataContext(ConnectString);
    var result = from d in db.Dogs
             join b in db.Breeds on d.BreedId equals b.BreedId
             select new
             {
                Name = d.Name,
                BreedName = b.BreedName
             }.ToList();

    return result.Select(r => (r.Name, r.BreedName)).ToList();
}

您可能需要安装System。ValueTuple nuget包。

您可以返回匿名类型，但这并不漂亮。

在这种情况下，我认为创建适当的类型会更好。如果只打算从包含该方法的类型中使用它，则将其设置为嵌套类型。

就我个人而言，我希望c#能够获得“命名匿名类型”——即与匿名类型相同的行为，但是有名称和属性声明，仅此而已。

EDIT: Others are suggesting returning dogs, and then accessing the breed name via a property path etc. That's a perfectly reasonable approach, but IME it leads to situations where you've done a query in a particular way because of the data you want to use - and that meta-information is lost when you just return IEnumerable<Dog> - the query may be expecting you to use (say) Breed rather than Ownerdue to some load options etc, but if you forget that and start using other properties, your app may work but not as efficiently as you'd originally envisaged. Of course, I could be talking rubbish, or over-optimising, etc...

这并没有完全回答你的问题，但谷歌根据关键字引导我到这里。这是从列表中查询匿名类型的方法:

var anon = model.MyType.Select(x => new { x.Item1, x.Item2});