Meziantou.Framework.SimpleQueryLanguage 1.0.9

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)
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