README.md

LHS Bracket Parser in C#

This is a simple parser for LHS Bracket syntax.

Install from Nuget:

Install LhsBracketParser Package by running this command in Package Manager Console:

Install-Package LhsBracketParser -Version 1.0.3

Why is this created at first place?

We needed some advanced filtering in our ASP.NET WebApi based project. I couldn't find any good library to turn predicates like (CreateDate[lt]2018-12-20 or Creator[eq]"Jalal") and IsNew[eq]true to an ORM based predicate.

I have already implemented an Evaluator for LLBLGen PredicateExpression type. You can implement your own by inheriting from EvaluatorBase class.

How it works?

In your application, get filter from query string and apply it to your repository like sample below. I am using LLBLGen as ORM so I instantiate PredicateExpressionEvaluator but you can implement your own by extending EvaluatorBase for EntityFramework or NHibernate.

// https://mysite.com/products?filter=(CreateDate[lt]2018-12-20 or Creator[eq]"Jalal") and IsNew[eq]true

[HttpGet]
public IActionResult Get(string filter)
{
    var evaluator = new PredicateExpressionEvaluator();
    var predicate = (PredicateExpression)evaluator.Evaluate(filter);
    
    var entities = repository.GetCollectionBy(predicate);
    
    /// ...
}

Notations

Operator	Bracket Notation
N/A	[range]
N/A	[like]
=	[eq]
!=	[ne]
>	[gt]
>=	[gte]
<	[lt]
<=	[lte]
and	and
or	or