Sorting by Reflection using GetProperty

Question

I have a generic class with a method that needs to sort a generic entity.

However, an error occurs saying that it does not recognize the Reflection GetProperty method, since lambda can not translate.

How can I do this sort ordering logic?

public IEnumerable<TEntity> GetAll()
{
    var obj = _repository.GetAll()
        .OrderByDescending(x => x.GetType().GetProperty(typeof(TEntity).Name + "Id"));

    return obj.Pagination();
}

Here is the error image:

Shortly: you need a helper which does order by string variable, like in [How to use a string to create a EF order by expression?](https://stackoverflow.com/questions/39908403/how-to-use-a-string-to-create-a-ef-order-by-expression), [Dynamic LINQ OrderBy on IEnumerable](https://stackoverflow.com/questions/41244/dynamic-linq-orderby-on-ienumerablet), [DynamicLINQ](https://github.com/kahanu/System.Linq.Dynamic) package etc. — Ivan Stoev, Jun 24 '17 at 08:22

score 0 · Answer 1 · answered Jun 24 '17 at 06:12

The error says it all.

Linq to Entities doesn't know how to translate x.GetType().GetProperty(typeof(TEntity).Name + "Id") into SQL.

You can materialize the results first, so it'll be linq to objects:

_repository.GetAll().ToList()
    .OrderByDescending(x => x.GetType().GetProperty(typeof(TEntity).Name + "Id"));

score 0 · Answer 2 · answered Jun 25 '17 at 03:38

0

You can use _repository.GetAll().Queryable().OrderByDescending(x => x.GetType().GetProperty(typeof(TEntity).Name + "Id"));

answered Jun 25 '17 at 03:38

DD84

313
1
6
15

score 0 · Answer 3 · answered Jun 25 '17 at 05:53

To build a LINQ query dynamically, use Expression Trees. This is how your method may look like:

public IEnumerable<TEntity> GetAll()
{
    IQueryable<TEntity> obj = _repository.GetAll();
    PropertyInfo keyProperty = typeof(TEntity).GetProperty(string.Concat(typeof(TEntity).Name, "Id"));
    Expression parameter = Expression.Parameter(typeof(TEntity));
    Expression predicate = Expression.Lambda(Expression.Property(parameter, keyProperty), parameter);
    Expression queryExpression = Expression.Call(typeof(Queryable), "OrderByDescending", new Type[] { typeof(TEntity), keyProperty.PropertyType }, obj, predicate);
    obj = obj.Provider.CreateQuery<TEntity>(queryExpression);
    return obj.Pagination();
}

Sorting by Reflection using GetProperty

3 Answers3