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README.md

Invio.Hashing

Build status Travis CI NuGet Coverage

A basic implementation for generating hash codes and determing equality for data objects.

Installation

The latest version of this package is available on NuGet. To install, run the following command:

PM> Install-Package Invio.Hashing

Usage

This package resolves around a single class: HashCode. By calling one of its From implementations, a caller can get consistent hash codes from an unbounded collection of objects, like so:

using Invio.Hashing;

var myHashCode = HashCode.From(123, "456", null, new List<Guid> { Guid.NewGuid() });

It is intended for use within data objects, like so:

using System;
using Invio.Hashing;

namespace MyNamespace {

    public class MyClass : IEquatable<MyClass> {

        public String MyProperty { get; set; }
        public int MyField;

        public override bool Equals(Object that) {
            return this.Equals(that as MyClass);
        }

        public override bool Equals(MyClass that) {
            return that != null
                && this.MyProperty == that.MyProperty
                && this.MyField == that.MyField;
        }

        public override int GetHashCode() {
            return HashCode.From(
                this.MyProperty,
                this.MyField
            );
        }

    }

}

The HashCode class also contains the FromList and FromSet implementations that allow a caller to pass in enumerables for which they want to generate hash codes that account for or ignore order, respectively. This is intended for use within data objects that contain enumerables, like so:

using System;
using System.Collections.Generic;
using Invio.Hashing;

namespace MyNamespace {

    public class MyClass : IEquatable<MyClass> {

        public IList<String> Tasks { get; } = new List<String>();
        public ISet<String> Tools { get; } = new HashSet<String>();

        public override bool Equals(Object that) {
            return this.Equals(that as MyClass);
        }

        public override bool Equals(MyClass that) {
            return that != null
                && this.Tasks.SequenceEqual(that.Tasks)
                && this.Tools.SetEquals(that.Tools);
        }

        public override int GetHashCode() {
            return HashCode.From(
                HashCode.FromList(this.Tasks),
                HashCode.FromSet(this.Tools)
            );
        }

    }

}

For situations where you wish to avoid using the default GetHashCode() implementation for a given object, you can use one of the overloads for FromList() or FromSet() that take in an IEqualityComparer implementation. This is especially helpful in scenarios when comparing strings that respect case-insensivity, like so:

using System;
using System.Collections.Generic;
using Invio.Hashing;

namespace MyNamespace {

    public class MyClass : IEquatable<MyClass> {

        private static StringComparer comparer { get; } = StringComparer.OrdinalIgnoreCase;

        public String CaseInsensitiveName { get; }
        public IList<String> CaseInsensitiveItems { get; } = new List<String>();

        public MyClass(String caseInsensitiveName) {
            this.CaseInsensitiveName = caseInsensitiveName;
        }

        public override bool Equals(Object that) {
            return this.Equals(that as MyClass);
        }

        public override bool Equals(MyClass that) {
            return that != null
                && comparer.Equals(this.CaseInsensitiveName, that.CaseInsensitiveName)
                && this.CaseInsensitiveItems.SequenceEqual(that.CaseInsensitiveTasks, comparer);
        }

        public override int GetHashCode() {
            return HashCode.From(
                comparer.GetHashCode(this.CaseInsensitiveName),
                HashCode.FromList(this.CaseInsensitiveItems, comparer)
            );
        }

    }

}

There's also an IfStringComparer implementation that will take in all objects (instead of exclusively Strings) and only performs case-specific behaviors if the type being evaluated in a String.

That's it. <3

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