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Meziantou.Framework.SimpleQueryLanguage

Syntax inspired from KQL (specification)

Usage

var collection = new List<Person>();

var queryBuilder = new QueryBuilder<Person>();
queryBuilder.AddHandler<string>("name", (obj, value) => obj.FullName.Contains(value, StringComparison.OrdinalIgnoreCase));
queryBuilder.AddRangeHandler<int>("age", (obj, value) => value.IsInRange((int)(DateTime.UtcNow - obj.DateOfBirth).TotalDays / 365));

var query = queryBuilder.Build("name:sample query");
query.Evaluate(new Person("John Doe", new DateTime(2000, 1, 1)));

record Person(string FullName, DateTime DateOfBirth);

Syntax

  • Logical operators NOT, AND, OR
  • Priority using (, )
  • AddHandler: supported operators: :
  • AddRangeHandler: supported operators: :, <, <=, >, >=, .. (range)
  • SetTextFilterHandler matches all non-bound filters
  • Special values: today, yesterday, this week, this month, last month, this year, last year

Examples:

  • name:john or name=john
  • name:"john doe"
  • name<>john or -name:john or NOT name:john
  • (name:"john doe" OR name:jane) AND age>21
  • created:"this week"
  • age:13..19 (lower and upper bound are included)
  • age>=21
  • is_open:true free form text
  • is_open:true AND NOT "free form text"

Expression-based queries for EF Core

The ExpressionQueryBuilder<T> class creates Expression<Func<T, bool>> objects that can be translated to SQL by Entity Framework Core, allowing you to apply query language filters directly to database queries.

// Define a query builder for your entity
var queryBuilder = new ExpressionQueryBuilder<Person>();

// Add handlers for string properties (uses Contains for partial matching).
// Case sensitivity follows the provider: the database collation for EF Core, ordinal for LINQ to Objects.
// Pass a StringComparison to force one, but note that EF Core cannot translate it.
queryBuilder.AddHandler("name", person => person.FullName);

// Add handlers for comparable types (supports range and comparison operators)
queryBuilder.AddHandler<int>("age", person => person.Age);
queryBuilder.AddHandler<DateTime>("created", person => person.CreatedAt);

// Optional: handle free-text search across multiple fields
queryBuilder.SetFreeTextHandler(text =>
    person => person.FullName.Contains(text) || person.Email.Contains(text));

// Build the query
var query = queryBuilder.Build("name:john AND age>=21");

// Apply to an IQueryable (e.g., EF Core DbSet)
var results = await dbContext.People
    .Apply(query)
    .ToListAsync();

The ExpressionQueryBuilder<T> supports the same query syntax as QueryBuilder<T>, including:

  • String matching with : operator
  • Comparison operators: <, <=, >, >=
  • Range syntax: age:18..25
  • Logical operators: AND, OR, NOT
  • Parentheses for grouping