How to dynamically order by certain entity properties in Entity Framework 7 (Core)

Question

I have a project where the front-end JavaScript specifies a list of columns to order by.

Then in the back-end I have multi-layer application. Typical scenario

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Answer 1

FromSql definitely cannot be used to mix SQL. So as usual with dynamic queries, you have to resort to System.Linq.Expressions.

For instance, something like this:

public static class QueryableExtensions
{
    public static IQueryable OrderBy(this IQueryable source, IEnumerable sortModels)
    {
        var expression = source.Expression;
        int count = 0;
        foreach (var item in sortModels)
        {
            var parameter = Expression.Parameter(typeof(T), "x");
            var selector = Expression.PropertyOrField(parameter, item.ColId);
            var method = string.Equals(item.Sort, "desc", StringComparison.OrdinalIgnoreCase) ?
                (count == 0 ? "OrderByDescending" : "ThenByDescending") :
                (count == 0 ? "OrderBy" : "ThenBy");
            expression = Expression.Call(typeof(Queryable), method,
                new Type[] { source.ElementType, selector.Type },
                expression, Expression.Quote(Expression.Lambda(selector, parameter)));
            count++;
        }
        return count > 0 ? source.Provider.CreateQuery(expression) : source;
    }
}

And then:

var thingsQuery = _context.Things
        .Include(t => t.Other)
        .Where(t => t.Deleted == false)
        .OrderBy(sortModels);