Sortable By Attribute

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public class SortableAttribute : Attribute
{
    public string EntityName { get; set; }

    public bool Default { get; set; }
}

public class SortTerm
{
    public string Name { get; set; }

    public string EntityName { get; set; }

    public bool Descending { get; set; }

    public bool Default { get; set; }
}

public class SortOptionsProcessor<Model, Entity>
{
    private readonly string[] _sort;

    public SortOptionsProcessor(string[] sortArray)
    {
        _sort = sortArray;
    }

    public IEnumerable<SortTerm> GetTerms()
    {
        if (_sort == null)
        {
            yield break;
        }

        foreach (var s in _sort)
        {
            if (string.IsNullOrEmpty(s))
            {
                continue;
            }

            var arr = s.Split(' ');

            if (arr.Length > 1)
            {
                yield return new SortTerm
                {
                    Name = arr[0],
                    EntityName = arr[0],
                    Descending = arr[1].Equals("desc", StringComparison.OrdinalIgnoreCase),
                    Default = false
                };
            }
            else
            {
                yield return new SortTerm
                {
                    Name = s,
                    EntityName = s,
                    Descending = false,
                    Default = false
                };
            }
        }
    }

    public IEnumerable<SortTerm> GetValidTerms()
    {
        var terms = GetTerms().ToArray();

        if (terms.Any())
        {
            var termsFromModel = GetModelTerms();

            foreach (var t in terms)
            {
                var term = termsFromModel.SingleOrDefault(v => v.Name.Equals(t.Name, StringComparison.OrdinalIgnoreCase));

                if (term == null)
                {
                    continue;
                }

                yield return new SortTerm
                {
                    Name = term.Name,
                    EntityName = term.EntityName,
                    Descending = t.Descending,
                    Default = term.Default
                };
            }
        }
    }

    public IEnumerable<SortTerm> GetModelTerms()
    {
        return typeof(Model).GetTypeInfo().DeclaredProperties
            .Where(v => v.GetCustomAttributes<SortableAttribute>().Any())
            .Select(v => new SortTerm
            {
                Name = v.Name,
                EntityName = v.GetCustomAttribute<SortableAttribute>().EntityName,
                Descending = false,
                Default = v.GetCustomAttribute<SortableAttribute>().Default
            });
    }

    public IQueryable<Entity> Process(IQueryable<Entity> queryable)
    {
        var terms = GetValidTerms().ToArray();

        if (terms.Any() == false)
        {
            terms = GetModelTerms().Where(v => v.Default).ToArray();
        }

        if (terms.Any() == false)
        {
            return queryable;
        }

        var useThenBy = false;

        foreach (var t in terms)
        {
            var propertyInfo = ExpressionHelper.GetPropertyInfo<Entity>(t.EntityName ?? t.Name);

            var parameterExpr = ExpressionHelper.Parameter<Entity>();

            var memberExpr = ExpressionHelper.GetPropertyExpression(parameterExpr, propertyInfo);

            var lambdaExpr = ExpressionHelper.GetLambda(typeof(Entity), propertyInfo.PropertyType, parameterExpr, memberExpr);

            queryable = ExpressionHelper.CallOrderByOrThenBy(queryable, useThenBy, t.Descending, propertyInfo.PropertyType, lambdaExpr);

            useThenBy = true;
        }

        return queryable;
    }
}

public class SortOptions<Model, Entity> : IValidatableObject
{
    public string[] Sort { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        var processor = new SortOptionsProcessor<Model, Entity>(Sort);

        var terms = processor.GetTerms()
            .Select(v => v.Name)
            .Except(processor.GetValidTerms().Select(v => v.Name), StringComparer.OrdinalIgnoreCase);

        foreach (var t in terms)
        {
            yield return new ValidationResult($"Invalid sort term '{t}'.", new[] { nameof(Sort) });
        }
    }

    public IQueryable<Entity> Process(IQueryable<Entity> queryable)
    {
        return new SortOptionsProcessor<Model, Entity>(Sort).Process(queryable);
    }
}

public class MemberModel
{
    [Sortable(EntityName = nameof(Id), Default = true)]
    public int Id { get; set; }

    [Sortable(EntityName = nameof(Name))]
    public string Name { get; set; }
}

public class Member
{
    public int Id { get; set; }

    public string Name { get; set; }
}

[ApiController]
[Route("/members")]
public class MemberController : ControllerBase
{
    [HttpGet]
    public IActionResult Get([FromQuery]SortOptions<MemberModel, Member> sortOptions)
    {
        var members = new List<Member>
        {
            new Member { Id = 1, Name = "A" },
            new Member { Id = 3, Name = "B" },
            new Member { Id = 2, Name = "B" }
        }; 

        var queryable = members.AsQueryable();

        queryable = sortOptions.Process(queryable);

        return Ok(queryable.ToList());
    }
}

标签：Sortable,Name,get,Attribute,queryable,var,new,public
来源： https://www.cnblogs.com/xiaowangzhi/p/10738943.html