Meziantou.Framework.SimpleQueryLanguage 2.0.4

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). Use * for an open bound: 10..* is >=10 and *..10 is <=10
• SetTextFilterHandler matches all non-bound filters
• Special values: today, yesterday, this week, this month, last month, this year, last year. The two-word values also accept an underscore, which needs no quotes: this_week, this_month, last_month, this_year, last_year.
• Relative dates: @today, optionally followed by an offset in days (d) or weeks (w): @today-1w, @today+3d. The value is the start of that day in UTC and can be used wherever a date is expected, including range bounds.
• Special values and relative dates are resolved when the query is built, so rebuild a query that is kept across days.

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" or created:this_week
• age:13..19 (lower and upper bound are included)
• stars:10..* or created:*..2024-12-31 (open bound)
• created>@today-1w or created:@today-2w..@today
• 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