Sieve is a simple, clean, and extensible framework for .NET Core that adds sorting, filtering, and pagination functionality out of the box. Most common use case would be for serving ASP.NET Core GET queries.

Programming language: C#
License: GNU General Public License v3.0 or later
Tags: NetCore     CLI     Netstandard     AspNetCore    

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⚗️ Sieve is a simple, clean, and extensible framework for .NET Core that adds sorting, filtering, and pagination functionality out of the box. Most common use case would be for serving ASP.NET Core GET queries.

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Usage for ASP.NET Core

In this example, consider an app with a Post entity. We'll use Sieve to add sorting, filtering, and pagination capabilities when GET-ing all available posts.

1. Add required services

Inject the SieveProcessor service. So in Startup.cs add:


2. Tell Sieve which properties you'd like to sort/filter in your models

Sieve will only sort/filter properties that have the attribute [Sieve(CanSort = true, CanFilter = true)] on them (they don't have to be both true). So for our Post entity model example:

public int Id { get; set; }

[Sieve(CanFilter = true, CanSort = true)]
public string Title { get; set; }

[Sieve(CanFilter = true, CanSort = true)]
public int LikeCount { get; set; }

[Sieve(CanFilter = true, CanSort = true)]
public int CommentCount { get; set; }

[Sieve(CanFilter = true, CanSort = true, Name = "created")]
public DateTimeOffset DateCreated { get; set; } = DateTimeOffset.UtcNow;

There is also the Name parameter that you can use to have a different name for use by clients.

Alternatively, you can use Fluent API to do the same. This is especially useful if you don't want to use attributes or have multiple APIs.

3. Get sort/filter/page queries by using the Sieve model in your controllers

In the action that handles returning Posts, use SieveModel to get the sort/filter/page query. Apply it to your data by injecting SieveProcessor into the controller and using its Apply<TEntity> method. So for instance:

public JsonResult GetPosts(SieveModel sieveModel) 
    var result = _dbContext.Posts.AsNoTracking(); // Makes read-only queries faster
    result = _sieveProcessor.Apply(sieveModel, result); // Returns `result` after applying the sort/filter/page query in `SieveModel` to it
    return Json(result.ToList());

You can also explicitly specify if only filtering, sorting, and/or pagination should be applied via optional arguments.

4. Send a request

Send a request

Add custom sort/filter methods

If you want to add custom sort/filter methods, inject ISieveCustomSortMethods or ISieveCustomFilterMethods with the implementation being a class that has custom sort/filter methods that Sieve will search through.

For instance:

services.AddScoped<ISieveCustomSortMethods, SieveCustomSortMethods>();
services.AddScoped<ISieveCustomFilterMethods, SieveCustomFilterMethods>();

Where SieveCustomSortMethodsOfPosts for example is:

public class SieveCustomSortMethods : ISieveCustomSortMethods
    public IQueryable<Post> Popularity(IQueryable<Post> source, bool useThenBy, bool desc) // The method is given an indicator of whether to use ThenBy(), and if the query is descending 
        var result = useThenBy ?
            ((IOrderedQueryable<Post>)source).ThenBy(p => p.LikeCount) : // ThenBy only works on IOrderedQueryable<TEntity>
            source.OrderBy(p => p.LikeCount)
            .ThenBy(p => p.CommentCount)
            .ThenBy(p => p.DateCreated);

        return result; // Must return modified IQueryable<TEntity>

    public IQueryable<T> Oldest<T>(IQueryable<T> source, bool useThenBy, bool desc) where T : BaseEntity // Generic functions are allowed too
        var result = useThenBy ?
            ((IOrderedQueryable<T>)source).ThenByDescending(p => p.DateCreated) :
            source.OrderByDescending(p => p.DateCreated);

        return result;

And SieveCustomFilterMethods:

public class SieveCustomFilterMethods : ISieveCustomFilterMethods
    public IQueryable<Post> IsNew(IQueryable<Post> source, string op, string[] values) // The method is given the {Operator} & {Value}
        var result = source.Where(p => p.LikeCount < 100 &&
                                        p.CommentCount < 5);

        return result; // Must return modified IQueryable<TEntity>

    public IQueryable<T> Latest<T>(IQueryable<T> source, string op, string[] values) where T : BaseEntity // Generic functions are allowed too
        var result = source.Where(c => c.DateCreated > DateTimeOffset.UtcNow.AddDays(-14));
        return result;

Configure Sieve

Use the ASP.NET Core options pattern with SieveOptions to tell Sieve where to look for configuration. For example:


Then you can add the configuration:

    "Sieve": {
        "CaseSensitive": "boolean: should property names be case-sensitive? Defaults to false",
        "DefaultPageSize": "int number: optional number to fallback to when no page argument is given. Set <=0 to disable paging if no pageSize is specified (default).",
        "MaxPageSize": "int number: maximum allowed page size. Set <=0 to make infinite (default)",
        "ThrowExceptions": "boolean: should Sieve throw exceptions instead of silently failing? Defaults to false",
        "IgnoreNullsOnNotEqual": "boolean: ignore null values when filtering using is not equal operator? Default to true"

Send a request

With all the above in place, you can now send a GET request that includes a sort/filter/page query. An example:

GET /GetPosts

?sorts=     LikeCount,CommentCount,-created         // sort by likes, then comments, then descendingly by date created 
&filters=   LikeCount>10, [email protected]=awesome title,     // filter to posts with more than 10 likes, and a title that contains the phrase "awesome title"
&page=      1                                       // get the first page...
&pageSize=  10                                      // ...which contains 10 posts

More formally:

  • sorts is a comma-delimited ordered list of property names to sort by. Adding a - before the name switches to sorting descendingly.
  • filters is a comma-delimited list of {Name}{Operator}{Value} where
    • {Name} is the name of a property with the Sieve attribute or the name of a custom filter method for TEntity
      • You can also have multiple names (for OR logic) by enclosing them in brackets and using a pipe delimiter, eg. (LikeCount|CommentCount)>10 asks if LikeCount or CommentCount is >10
    • {Operator} is one of the Operators
    • {Value} is the value to use for filtering
      • You can also have multiple values (for OR logic) by using a pipe delimiter, eg. [email protected]=new|hot will return posts with titles that contain the text "new" or "hot"
  • page is the number of page to return
  • pageSize is the number of items returned per page


  • You can use backslashes to escape commas and pipes within value fields
  • You can have spaces anywhere except within {Name} or {Operator} fields
  • If you need to look at the data before applying pagination (eg. get total count), use the optional paramters on Apply to defer pagination (an example)
  • Here's a good example on how to work with enumerables
  • Another example on how to do OR logic

Nested objects

You can filter/sort on a nested object's property by marking the property using the Fluent API. Marking via attributes not currently supported.

For example, using this object model:

public class Post {
    public User Creator { get; set; }

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

Mark Post.User to be filterable:

// in MapProperties
mapper.Property<Post>(p => p.Creator.Name)

Now you can make requests such as: filters=User.Name==specific_name.

Creating your own DSL

You can replace this DSL with your own (eg. use JSON instead) by implementing an ISieveModel. You can use the default SieveModel for reference.


Operator Meaning
== Equals
!= Not equals
> Greater than
< Less than
>= Greater than or equal to
<= Less than or equal to
@= Contains
_= Starts with
[email protected]= Does not Contains
!_= Does not Starts with
@=* Case-insensitive string Contains
_=* Case-insensitive string Starts with
==* Case-insensitive string Equals
!=* Case-insensitive string Not equals
[email protected]=* Case-insensitive string does not Contains
!_=* Case-insensitive string does not Starts with

Handle Sieve's exceptions

Sieve will silently fail unless ThrowExceptions in the configuration is set to true. 3 kinds of custom exceptions can be thrown:

  • SieveMethodNotFoundException with a MethodName
  • SieveIncompatibleMethodException with a MethodName, an ExpectedType and an ActualType
  • SieveException which encapsulates any other exception types in its InnerException

It is recommended that you write exception-handling middleware to globally handle Sieve's exceptions when using it with ASP.NET Core.

Example project

You can find an example project incorporating most Sieve concepts in SieveTests.

Fluent API

To use the Fluent API instead of attributes in marking properties, setup an alternative SieveProcessor that overrides MapProperties. For example:

public class ApplicationSieveProcessor : SieveProcessor
    public ApplicationSieveProcessor(
        IOptions<SieveOptions> options, 
        ISieveCustomSortMethods customSortMethods, 
        ISieveCustomFilterMethods customFilterMethods) 
        : base(options, customSortMethods, customFilterMethods)

    protected override SievePropertyMapper MapProperties(SievePropertyMapper mapper)
        mapper.Property<Post>(p => p.Title)

        mapper.Property<Post>(p => p.CommentCount)

        mapper.Property<Post>(p => p.DateCreated)

        return mapper;

Now you should inject the new class instead:

services.AddScoped<ISieveProcessor, ApplicationSieveProcessor>();

Find More on Sieve's Fluent API here.

Upgrading to v2.2.0

2.2.0 introduced OR logic for filter values. This means your custom filters will need to accept multiple values rather than just the one.

  • In all your custom filter methods, change the last argument to be a string[] values instead of string value
  • The first value can then be found to be values[0] rather than value
  • Multiple values will be present if the client uses OR logic

Upgrading from v1.* to v2.*

  • Changes to the SieveProcessor API:
    • ApplyAll is now Apply
    • ApplyFiltering, ApplySorting, and ApplyPagination are now depricated - instead you can use optional arguments on Apply to achieve the same
  • Instead of just removing commas from {Value}s, you'll also need to remove brackets and pipes

License & Contributing

Sieve is licensed under Apache 2.0. Any contributions highly appreciated!

*Note that all licence references and agreements mentioned in the Sieve README section above are relevant to that project's source code only.