Is it possible to Sort on multiple fields?

[AdamAdu3]

Hi there,

I'm currently using AutoFilterer for paging and filtering and would like to get sorting working. While working on implementing this, I noticed that Sort and SortBy is only supported on a single field. Is it possible to sort on multiple fields without writing custom Expressions?

[enisn]

It's a good point. Filtering multiple fields in a single field is not Open API Specs friendly and it's not supported by AutoFilterer by default. But I can share an example code that helps you to achieve this goal.

1. Create your own FilterBase class

public class MultipleSortingFilterBase : PaginationFilterBase
{
    public override IOrderedQueryable<TSource> ApplyOrder<TSource>(IQueryable<TSource> source)
    {
        // books?sort=title asc,totalPage desc

        var sortings = this.Sort.Split(',');

        var query = source;

        for (int i = 0; i < sortings.Length; i++)
        {
            if (i == 0)
            {
                query = ApplyOrderBy(query, sortings[i].Split(' ').First(), sortings[i].EndsWith("desc"));
            }
            else
            {
                query = ApplyThenBy(query as IOrderedQueryable<TSource>, sortings[i].Split(' ').First(), sortings[i].EndsWith("desc"));
            }
        }

        return query as IOrderedQueryable<TSource>;
    }

    private static readonly MethodInfo orderBy = typeof(Queryable).GetMethods().First(x => x.Name == nameof(Queryable.OrderBy));
    private static readonly MethodInfo orderByDescending = typeof(Queryable).GetMethods().First(x => x.Name == nameof(Queryable.OrderByDescending));
    private static readonly MethodInfo thenBy = typeof(Queryable).GetMethods().First(x => x.Name == nameof(Queryable.ThenBy));
    private static readonly MethodInfo thenByDescending = typeof(Queryable).GetMethods().First(x => x.Name == nameof(Queryable.ThenByDescending));

    private IOrderedQueryable<TSource> ApplyOrderBy<TSource>(IQueryable<TSource> source, string propertyName, bool descending)
    {
        var parameter = Expression.Parameter(typeof(TSource), "o");
        var property = GetMemberExpression(parameter, propertyName);
        var lambda = Expression.Lambda(property, parameter);

        if (descending)
        {
            return orderByDescending.MakeGenericMethod(typeof(TSource), property.Type)
                .Invoke(null, parameters: new object[] { source, lambda }) as IOrderedQueryable<TSource>;
        }

        return orderBy.MakeGenericMethod(typeof(TSource), property.Type)
                .Invoke(null, parameters: new object[] { source, lambda }) as IOrderedQueryable<TSource>;
    }

    private IOrderedQueryable<TSource> ApplyThenBy<TSource>(IOrderedQueryable<TSource> source, string propertyName, bool descending)
    {
        var parameter = Expression.Parameter(typeof(TSource), "o");
        var property = GetMemberExpression(parameter, propertyName);
        var lambda = Expression.Lambda(property, parameter);

        if (descending)
        {
            return thenByDescending.MakeGenericMethod(typeof(TSource), property.Type)
                .Invoke(null, parameters: new object[] { source, lambda }) as IOrderedQueryable<TSource>;
        }

        return thenBy.MakeGenericMethod(typeof(TSource), property.Type)
                .Invoke(null, parameters: new object[] { source, lambda }) as IOrderedQueryable<TSource>;
    }

    private static MemberExpression GetMemberExpression(Expression parameter, string name)
    {
        if (!name.Contains("."))
            return Expression.Property(parameter, name);

        var expression = parameter;
        foreach (var item in name.Split('.'))
        {
            expression = GetMemberExpression(expression, item);
        }

        return expression as MemberExpression;
    }
}

2. Then inherit your filter dto from the new class:

public class BookFilter : MultipleSortingFilterBase
{
	// ...
}

3. See the result:
   

[enisn]

You can combine however you want after this implementation: