Quaero

A web-friendly query language that transforms into Microsoft Graph, Active Directory, and SCIM filters

What is Quaero?

Quaero is a small, intuitive query language designed to unify filtering across different systems. Instead of learning multiple query syntaxes for Microsoft Graph, LDAP, and SCIM, you write queries once in Quaero and transform them into the target system's native filter format.

Key Benefits:

• Universal syntax - Write queries once, use everywhere
• Web-friendly - Uses readable operators like eq, gt, and instead of symbols
• Type-safe - Built for .NET with strong typing support
• Optimizable - Automatic query optimization removes redundancies

Quick Start

Installation

# Core library
dotnet add package Quaero

# Target-specific packages
dotnet add package Quaero.MicrosoftGraph
dotnet add package Quaero.Ldap  
dotnet add package Quaero.Scim

Basic Usage

using Quaero;

// Parse a filter from string
Filter filter = Filter.Parse("age gt 42 and department eq \"Engineering\"");

// Or build programmatically
Filter filter = Filter.And(
    Filter.GreaterThan("age", 42),
    Filter.Equals("department", "Engineering")
);

// Transform to target system
string microsoftGraph = filter.ToMicrosoftGraphFilter();
string ldapFilter = filter.ToLdapFilter(); 
string scimFilter = filter.ToScimFilter();

// Use in-memory
Func<Employee, bool> predicate = filter.ToPredicate<Employee>();

Supported Operators

Operator	Description	Example
eq	Equals	name eq "John"
ne	Not equals	status ne "inactive"
gt	Greater than	age gt 21
ge	Greater than or equal	salary ge 50000
lt	Less than	score lt 100
le	Less than or equal	rating le 5
sw	Starts with	email sw "admin"
ew	Ends with	domain ew ".com"
co	Contains	title co "Manager"
in	In list	status in ["active", "pending"]
pr	Present (not null)	phoneNumber pr
and	Logical AND	age gt 18 and verified eq true
or	Logical OR	role eq "admin" or role eq "moderator"
not	Logical NOT	not(status eq "deleted")

Translation Examples

Here's how the same Quaero query translates across different systems:

System	Query
Quaero	age gt 42 and department eq "Engineering"
Microsoft Graph	age gt 42 and department eq 'Engineering'
LDAP	(&(age>=43)(department=Engineering))
SCIM	age gt 42 and department eq "Engineering"

Complex Query Example

// Quaero query
string query = @"(department in [""Sales"", ""Marketing""] and salary ge 75000) 
                 or (role eq ""Senior Developer"" and experience gt 5)";

Filter filter = Filter.Parse(query);

// Microsoft Graph: ((department in ('Sales', 'Marketing') and salary ge 75000) or (role eq 'Senior Developer' and experience gt 5))
// LDAP: (|((&(|(department=Sales)(department=Marketing))(salary>=75000))(&(role=Senior Developer)(experience>=6))))
// SCIM: (department in ["Sales", "Marketing"] and salary ge 75000) or (role eq "Senior Developer" and experience gt 5)

Advanced Features

Query Optimization

Filter filter = Filter.Parse("name eq \"John\" and name eq \"John\"");
Filter optimized = filter.Optimize(); // Removes redundant conditions

In-Memory Evaluation

record Employee(string Name, int Age, string Department);

var employees = new List<Employee> 
{
    new("Alice", 30, "Engineering"),
    new("Bob", 45, "Sales"),
    new("Carol", 28, "Engineering")
};

Filter filter = Filter.Parse("age gt 35 or department eq \"Engineering\"");
Func<Employee, bool> predicate = filter.ToPredicate<Employee>();

var results = employees.Where(predicate).ToList();
// Returns: Alice, Bob, Carol

Error Handling

// Safe parsing
if (Filter.TryParse("invalid query", out Filter? filter))
{
    // Success
    string result = filter.ToMicrosoftGraphFilter();
}
else
{
    // Handle parse error
    Console.WriteLine("Invalid query syntax");
}

Sponsors

Entity Framework Extensions and Dapper Plus are major sponsors and proud to contribute to the development of Quaero.