QueryKit 🎛️

QueryKit is a .NET library that makes it easier to query your data by providing a fluent and intuitive syntax for filtering and sorting. The main use case is a lighter weight subset of OData or GraphQL for parsing external filtering and sorting inputs to provide more granular consumption (e.g. a React UI provides filtering controls to filter a worklist). It's inspired by Sieve, but with some differences.

Getting Started

dotnet add package QueryKit

If we wanted to apply a filter to a DbSet called People, we just have to do something like this:

var filterInput = """FirstName == "Jane" && Age > 10""";
var people = _dbContext.People
  	.ApplyQueryKitFilter(filterInput)
  	.ToList();

QueryKit will automatically translate this into an expression for you. You can even customize your property names:

var filterInput = """first == "Jane" && Age > 10""";
var config = new QueryKitConfiguration(config =>
{
    config.Property<Person>(x => x.FirstName).HasQueryName("first");
});
var people = _dbContext.People
  	.ApplyQueryKitFilter(filterInput, config)
  	.ToList();

Sorting works too:

var filterInput = """first == "Jane" && Age > 10""";
var config = new QueryKitConfiguration(config =>
{
    config.Property<Person>(x => x.FirstName).HasQueryName("first");
});
var people = _dbContext.People
  	.ApplyQueryKitFilter(filterInput, config)
  	.ApplyQueryKitSort("first, Age desc", config)
  	.ToList();

And that's the basics! There's no services to inject or global set up to worry about, just apply what you want and call it a day. For a full list of capables, see below.

Filtering

Usage

To apply filters to your queryable, you just need to pass an input string with your filtering input to ApplyQueryKitFilter off of a queryable:

var people = _dbContext.People.ApplyQueryKitFilter("Age < 10").ToList();

You can also pass a configuration like this. More on configuration options below.

var config = new QueryKitConfiguration(config =>
{
    config.Property<SpecialPerson>(x => x.FirstName)
     	 		.HasQueryName("first")
      		.PreventSort();
});
var people = _dbContext.People
  		.ApplyQueryKitFilter(@$"first == "Jane" && Age < 10", config)
  		.ToList();

Logical Operators

When filtering, you can use logical operators && for and as well as || for or. For example:

var input = """FirstName == "Jane" && Age < 10""";
var input = """FirstName == "Jane" || FirstName == "John" """;

Order of Operations

You can use order of operation with parentheses like this:

var input = """(FirstName == "Jane" && Age < 10) || FirstName == "John" """;

Comparison Operators

There's a wide variety of comparison operators that use the same base syntax as Sieve's operators. To do a case-insensitive operation, just append a * at the end of the operator.

Name	Operator	Case Insensitive Operator	Count Operator
Equals	==	==*	#==
Not Equals	!=	!=*	#!=
Greater Than	>	N/A	#>
Less Than	<	N/A	#<
Greater Than Or Equal	>=	N/A	#>=
Less Than Or Equal	<=	N/A	#<=
Starts With	_=	_=*	N/A
Does Not Start With	!_=	!_=*	N/A
Ends With	_-=	_-=*	N/A
Does Not End With	!_-=	!_-=*	N/A
Contains	@=	@=*	N/A
Does Not Contain	!@=	!@=*	N/A
Sounds Like	~~	N/A	N/A
Does Not Sound Like	!~	N/A	N/A
Has	^$	^$*	N/A
Does Not Have	!^$	!^$*	N/A
In	^^	^^*	N/A
Not In	!^^	!^^*	N/A

Sounds Like and Does Not Sound Like requires a soundex configuration on your DbContext. For more info see the docs below

Here's an example for the in operator:

var input = """(Age ^^ [20, 30, 40]) && (BirthMonth ^^* ["January", "February", "March"]) || (Id ^^ ["6d623e92-d2cf-4496-a2df-f49fa77328ee"])""";

Filtering Notes

• string and guid properties should be wrapped in double quotes

  • null doesn't need quotes: var input = "Title == null";

  • Double quotes can be escaped by using a similar syntax to raw-string literals introduced in C#11:

    var input = """""Title == """lamb is great on a "gee-ro" not a "gy-ro" sandwich""" """"";
    // OR 
    var input = """""""""Title == """"lamb is great on a "gee-ro" not a "gy-ro" sandwich"""" """"""""";

• Dates and times use ISO 8601 format and should be surrounded by double quotes:

  • DateOnly: var filterInput = """Birthday == "2022-07-01" """;

  • DateTimeOffset:

    • var filterInput = """Birthday == "2022-07-01T00:00:03Z" """;

  • DateTime: var filterInput = """Birthday == "2022-07-01" """;

    • var filterInput = """Birthday == "2022-07-01T00:00:03" """;
    • var filterInput = """Birthday == "2022-07-01T00:00:03+01:00" """;

  • TimeOnly:

    • var filterInput = """Time == "12:30:00" """;
    • var filterInput = """Time == "12:30:00.678722" """;

• bool properties need to use == true, == false, or the same using the != operator. they can not be standalone properies:

  • ❌ var input = """Title == "chicken & waffles" && Favorite""";
  • ✅ var input = """Title == "chicken & waffles" && Favorite == true""";

Complex Example

var input = """(Title == "lamb" && ((Age >= 25 && Rating < 4.5) || (SpecificDate <= "2022-07-01T00:00:03Z" && Time == "00:00:03")) && (Favorite == true || Email.Value _= "[email protected]"))""";

Filtering Collections

You can also filter into collections with QueryKit by using most of the normal operators. For example, if I wanted to filter for recipes that only have an ingredient named salt, I could do something like this:

var input = """"Ingredients.Name == "salt" """";

By default, QueryKit will use Any under the hood when building this filter, but if you want to use All, you just need to prefix the operator with a %:

var input = """"Ingredients.Stock %>= 1"""";

🚧 At the moment, nested collections like Ingredients.Suppliers.Rating > 4 is still under active development

If you want to filter a primitve collection like List<string> you can use the Has or DoesNotHave operator (can be case insensitive with the appended *):

var input = """Tags ^$ "winner" """;
// or
var input = """Tags !^$ "winner" """;

If you want to filter on the count of a collection, you can prefix some of the operators with a #. For example, if i wanted to get all recipes that have more than 0 ingredients:

var input = """"Ingredients #>= 0"""";

Filtering Enums

You can filter enums with their respective integer value:

var input = "BirthMonth == 1";

public enum BirthMonthEnum
{
    January = 1,
    February = 2,
	  //...
}

Settings

Property Settings

Filtering is set up to create an expression using the property names you have on your entity, but you can pass in a config to customize things a bit when needed.

• HasQueryName() to create a custom alias for a property. For exmaple, we can make FirstName aliased to first.
• PreventFilter() to prevent filtering on a given property

var input = $"""first == "Jane" || Age > 10""";
var config = new QueryKitConfiguration(config =>
{
    config.Property<SpecialPerson>(x => x.FirstName)
     	 		.HasQueryName("first");
    config.Property<SpecialPerson>(x => x.Age)
      		.PreventFilter();
});

Derived Properties

You can also expose custom derived properties for consumption. Just be sure that Linq can handle them in a db query if you're using it that way.

var config = new QueryKitConfiguration(config =>
{
    config.DerivedProperty<Person>(p => p.FirstName + " " + p.LastName).HasQueryName("fullname");
    config.DerivedProperty<Person>(p => p.Age >= 18 && p.FirstName == "John").HasQueryName("adult_johns");
});

var input = $"""(fullname @=* "John Doe") && age >= 18""";
// or
var input = $"""adult_johns == true""";

Custom Operators

You can also add custom comparison operators to your config if you'd like:

var config = new QueryKitConfiguration(config =>
{
    config.EqualsOperator = "@@$";
    config.CaseInsensitiveAppendix = "$";
    config.AndOperator = "and";
});

If you want to use it globally, you can make a base implementation like this:

public class CustomQueryKitConfiguration : QueryKitConfiguration
{
    public CustomQueryKitConfiguration(Action<QueryKitSettings>? configureSettings = null)
        : base(settings => 
        {
            settings.EqualsOperator = "eq";
            settings.NotEqualsOperator = "neq";
            settings.GreaterThanOperator = "gt";
            settings.GreaterThanOrEqualOperator = "gte";
            settings.LessThanOperator = "lt";
            settings.LessThanOrEqualOperator = "lte";
            settings.ContainsOperator = "ct";
            settings.StartsWithOperator = "sw";
            settings.EndsWithOperator = "ew";
            settings.NotContainsOperator = "nct";
            settings.NotStartsWithOperator = "nsw";
            settings.NotEndsWithOperator = "new";
            settings.AndOperator = "and";
            settings.OrOperator = "or";
            settings.CaseInsensitiveAppendix = "i";

            configureSettings?.Invoke(settings);
        })
    {
    }
}

// ---

var input = """Title eq$ "Pancakes" and Rating gt 10""";
var config = new CustomQueryKitConfiguration();
var filterExpression = FilterParser.ParseFilter<Recipe>(input, config);

Note Spaces must be used around the comparison operator when using custom values. Title @@$ "titilating" ✅ Title@@$"titilating" ❌

Allow Unknown Properties

By default, QueryKit will throw an error if it doesn't recognize a property name, If you want to loosen the reigns here a bit, you can set AllowUnknownProperties to true in your config. When active, unknown properties will be ignored in the expression resolution.

var config = new QueryKitConfiguration(config =>
{
    config.AllowUnknownProperties = true;
});
var filterExpression = FilterParser.ParseFilter<Recipe>(input, config);

Nested Objects

Say we have a nested object like this:

public class SpecialPerson
{
    public Guid Id { get; set; } = Guid.NewGuid();
    public EmailAddress Email { get; set; }
}

public class EmailAddress : ValueObject
{
    public EmailAddress(string? value)
    {
        Value = value;
    }
    
    public string? Value { get; private set; }
}

To actually use the nested properties, you can do something like this:

var input = $"""Email.Value == "{value}" """;

// or with an alias...
var input = $"""email == "[email protected]" """;
var config = new QueryKitConfiguration(config =>
{
    config.Property<SpecialPerson>(x => x.Email.Value).HasQueryName("email");
});

Note, with EF core, your config might look like this:

public sealed class PersonConfiguration : IEntityTypeConfiguration<SpecialPerson>
{
    public void Configure(EntityTypeBuilder<SpecialPerson> builder)
    {
        builder.HasKey(x => x.Id);
      
      	// Option 1 (as of .NET 8)
      	builder.ComplexProperty(x => x.Email,
            x => x.Property(y => y.Value)
                .HasColumnName("email")); 
      
      	// Option 2
        builder.Property(x => x.Email)
            .HasConversion(x => x.Value, x => new EmailAddress(x))
            .HasColumnName("email");      
      
        // Option 3   
        builder.OwnsOne(x => x.Email, opts =>
        {
            opts.Property(x => x.Value).HasColumnName("email");
        }).Navigation(x => x.Email)
            .IsRequired();
    }
}

Warning EF properties configured with HasConversion are not supported at this time

Sorting

Sorting is a more simplistic flow. It's just an input with a comma delimited list of properties to sort by.

Rules

• use asc or desc to designate if you want it to be ascending or descending. If neither is used, QueryKit will assume asc
• You can use Sieve syntax as well by prefixing a property with - to designate it as desc
• Spaces after commas are optional

So all of these are valid:

var input = "Title";
var input = "Title, Age desc";
var input = "Title desc, Age desc";
var input = "Title, Age";
var input = "Title asc, -Age";
var input = "Title, -Age";

Property Settings

Sorting is set up to create an expression using the property names you have on your entity, but you can pass in a config to customize things a bit when needed.

• Just as with filtering, HasQueryName() to create a custom alias for a property. For exmaple, we can make FirstName aliased to first.
• PreventSort() to prevent filtering on a given property

var input = $"""Age desc, first"";
var config = new QueryKitConfiguration(config =>
{
    config.Property<SpecialPerson>(x => x.FirstName)
          .HasQueryName("first")
          .PreventSort();
});

Aggregate QueryKit Application

If you want to apply filtering and sorting in one fell swoop, you can do something like this:

var config = new QueryKitConfiguration(config =>
{
    config.Property<Person>(x => x.FirstName).HasQueryName("first");
});
var people = _dbContext.People
  	.ApplyQueryKit(new QueryKitData() 
        {
            Filters = """first == "Jane" && Age > 10""",
            SortOrder = "first, Age desc",
            Configuration = config
        })
  	.ToList();

Error Handling

If you want to capture errors to easily throw a 400, you can add error handling around these exceptions:

• A QueryKitException is the base class for all of the exceptions listed below. This can be caught to catch any exception thrown by QueryKit.
• A ParsingException will be thrown when there is an invalid operator or bad syntax is used (e.g. not using double quotes around a string or guid).
• An UnknownFilterPropertyException will be thrown if a property is not recognized during filtering
• A SortParsingException will be thrown if a property or operation is not recognized during sorting
• A QueryKitDbContextTypeException will be thrown when trying to use a DbContext specific workflow without passing that context (e.g. SoundEx)
• A SoundsLikeNotImplementedException will be thrown when trying to use soundex on a DbContext that doesn't have it implemented.
• A QueryKitParsingException is a more generic error that will include specific details on a more granular error in the parsing pipeline.

SoundEx

The Sounds Like and Does Not Sound Like operators require a soundex configuration on any DbContext that contain your DbSet being filtered on. Something like the below should work. The SoundsLike method does not need to implement anything and is just used as a pointer to the db method.

public class ExampleDbContext : DbContext
{
    public ExampleDbContext(DbContextOptions<TestingDbContext> options)
        : base(options)
    {
    }
    
    [DbFunction (Name = "SOUNDEX", IsBuiltIn = true)]
    public static string SoundsLike(string query) => throw new NotImplementedException();

    public DbSet<People> MyPeople { get; set; }
    
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.HasPostgresExtension("fuzzystrmatch");
    }
}

⭐️ Note that with Postgres, something like modelBuilder.HasPostgresExtension("fuzzystrmatch"); will need to be added like the example along with a migration for adding the extension.

You can even use this on a normal IQueryable like this:

var waffleRecipes = _dbContext.MyPeople
  .Where(x => ExampleDbContext.SoundsLike(x.LastName) == ExampleDbContext.SoundsLike("devito"))
  .ToList();

Usage

Once your DbContext is configured to allow soundex, you'll need to provide that DbContext type in your QueryKit config. This is because, as of now, there is no reliable way to get the DbContext from an IQueryable.

var input = $"""LastName ~~ "devito" """;

// Act
var queryablePeople = testingServiceScope.DbContext().People;
var appliedQueryable = queryablePeople.ApplyQueryKitFilter(input, new QueryKitConfiguration(o =>
{
    o.DbContextType = typeof(TestingDbContext);
}));
var people = await appliedQueryable.ToListAsync();

Community Projects

• Fluent QueryKit for easy usage in javascript or typescript projects.