Quaero 0.1.0

Quaero

A small query language that can transform queries into system-specific filters.

Quaero is designed to be web-friendly by using letter-based operators instead of symbols. It's very similar to Microsoft Graph (OData) filters, with a few minor differences:

1. Infix not operators
2. Infix function operators

See example queries for some examples.

This repository contains translation implementations for Microsoft Graph and Active Directory (LDAP) filters, as well as in-memory predicates.

Supported operators

The language supports a wide range of operators supported by most filter/query languages.

Equality operators

• Equals (eq)
• Not equals (ne)
• Logical negation (not)
• In (in)

Relational operators

• Less than (lt)
• Greater than (gt)
• Less than or equal to (le)
• Greater than or equal to (ge)

Conditional operators

• And (and)
• Or (or)

Functions

• Starts with (startsWith)
• Ends with (endsWith)

Example queries

Usage

Either parse a filter expression from a string using Filter.Parse or Filter.TryParse:

Filter filter = Filter.Parse("age gt 42");

Or manually construct a filter expression using the factory methods on the Filter class:

Filter filter = Filter.GreaterThan("age", 42);

Once the filter has been successfully parsed, it can be optimized by calling the Optimize extension method. This will take care of removing redundancies and shortening the resulting query.

To transform the query into an LDAP filter, reference the Quaero.Ldap package and call the ToLdapFilter method on it:

string result = filter.ToLdapFilter();

For Microsoft Graph, reference the Quaero.MicrosoftGraph package and call ToMicrosoftGraphFilter on the filter:

string result = filter.ToMicrosoftGraphFilter();

If you want to evaluate a filter in-memory, you can call the ToPredicate<T> method on it:

record Person(string Name, int Age);
Func<Person, bool> predicate = filter.ToPredicate<Person>();