README.md

Pather.CSharp

Pather.CSharp - A Path Resolution Library for C#

Installation

Type in this command in Package Manager Console

PM> Install-Package Pather.CSharp

Basic Usage

Create a new Resolver and pass the object and path to its Resolve method.

IResolver resolver = new Resolver();
var o = new { Property1 = new { Property2 = "value" } };
var path = "Property1.Property2";

object result = r.Resolve(o, path); //the result is "value"

Possible Paths

Property, array (per index) and dictionary (per key) resolution are supported out of the box.

Examples

Property
Property1.Property2
ArrayProperty[5]
DictionaryProperty[Key]
[0] //just an array index
[Key] //just a dictionary index
NestedArray2
NestedDictionary[Key1][Key2]

Selections

Pather.CSharp can also operate on collections of objects. If you have an array of objects, and each has a property called P, you can access it and get the values of P for all objects in the array.
This behavior can be triggered using [] in the path on a IEnumerable.

For example:

var r = new Resolver();
var array = new[]
{
    new { P1 = "1" },
    new { P1 = "2" }
};
var path = "[].P1";

var result = r.Resolve(array, path);    
//result is a collection that contains the values "1" and "2"

Teaching Pather.CSharp new Tricks

Preamble

There are 2 interfaces you have to know about if you want to extend Pather.CSharp:

1. IPathElementFactory
2. IPathElement

IPathElementFactory has an IsApplicable method, which determines if it can create an IPathElement for the given path.
Its Create method creates an IPathElement object for the given path and outputs a new path, which is the old path stripped by the parts Create used to create the PathElement.

An example:

Input path    Property1.Property2
Output path .Property2

IPathElement only has an Apply method, which extracts an object from the given target.

The main class, Resolver, has a List of IPathElementFactory objects. It uses the first one that is applicable to create an IPathElement. These IPathElements are then applied in order on the target.

Extending Pather.CSharp

To extend it 3 steps are needed:

1. Create a class that implements IPathElement
2. Create a class that implements IPathElementFactory
3. Add an instance of your IPathElementFactory to the instance of Resolver

The naming convention is to name classes that implement IPathElement after what they do, and their factories with the suffix Factory.

For example: Property resolves property accessing, and PropertyFactory is its factory.

It is probably easiest to look at the existing implementations, to get some ideas how to implement it. They are very straightforward, DictionaryAccessFactory for example has only 7 (interesting) lines of code, the rest of the 27 LOC are boilerplate.