Add AmountOfSubstance.AvogadroConstant (#593)

Author: tmilnthorp

UnitsNet.Tests/CustomCode/AmountOfSubstanceTests.cs

@@ -21,6 +21,7 @@
 // Copyright 2013 Andreas Gullberg Larsen ([email protected]). Maintained at https://github.com/angularsen/UnitsNet.
 
 using System;
+using Xunit;
 
 namespace UnitsNet.Tests.CustomCode
 {
@@ -41,5 +42,21 @@ public class AmountOfSubstanceTests : AmountOfSubstanceTestsBase
         protected override double NanopoundMolesInOneMole => 0.002204622621848776 * 1e9;
         protected override double PoundMolesInOneMole => 0.002204622621848776;
         protected override double MegamolesInOneMole => 1e-6;
+
+        [Fact]
+        public void NumberOfParticlesInOneMoleEqualsAvogadroConstant()
+        {
+            var oneMole = AmountOfSubstance.FromMoles(1);
+            var numberOfParticles = oneMole.NumberOfParticles();
+            Assert.Equal(AmountOfSubstance.AvogadroConstant, numberOfParticles);
+        }
+
+        [Fact]
+        public void NumberOfParticlesInTwoMolesIsDoubleAvogadroConstant()
+        {
+            var twoMoles = AmountOfSubstance.FromMoles(2);
+            var numberOfParticles = twoMoles.NumberOfParticles();
+            Assert.Equal(AmountOfSubstance.AvogadroConstant * 2, numberOfParticles);
+        }
     }
 }

UnitsNet/CustomCode/Quantities/AmountOfSubstance.extra.cs

@@ -0,0 +1,55 @@
+// Copyright (c) 2013 Andreas Gullberg Larsen ([email protected]).
+// https://github.com/angularsen/UnitsNet
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+// ReSharper disable once CheckNamespace
+
+using UnitsNet.Units;
+
+namespace UnitsNet
+{
+    public partial struct AmountOfSubstance
+    {
+        /// <summary>
+        ///     The Avogadro constant is the number of constituent particles, usually molecules, 
+        ///     atoms or ions that are contained in the amount of substance given by one mole. It is the proportionality factor that relates 
+        ///     the molar mass of a substance to the mass of a sample, is designated with the symbol NA or L[1], and has the value 
+        ///     6.02214076e23 mol−1 in the International System of Units (SI).
+        /// </summary>
+        /// <remarks>
+        ///     Pending revisions in the base set of SI units necessitated redefinitions of the concepts of chemical quantity. The Avogadro number,
+        ///     and its definition, was deprecated in favor of the Avogadro constant and its definition. Based on measurements made through the
+        ///     middle of 2017 which calculated a value for the Avogadro constant of NA = 6.022140758(62)×1023 mol−1, the redefinition of SI units
+        ///     is planned to take effect on 20 May 2019. The value of the constant will be fixed to exactly 6.02214076×1023 mol−1.
+        ///     See here: https://www.bipm.org/utils/common/pdf/CGPM-2018/26th-CGPM-Resolutions.pdf
+        /// </remarks>
+        public static double AvogadroConstant { get; } = 6.02214076e23;
+
+        /// <summary>
+        /// Calculates the number of particles (atoms or molecules) in this amount of substance using the <see cref="AvogadroConstant"/>.
+        /// </summary>
+        /// <returns>The number of particles (atoms or molecules) in this amount of substance.</returns>
+        public double NumberOfParticles()
+        {
+            var moles = AsBaseNumericType(AmountOfSubstanceUnit.Mole);
+            return AvogadroConstant * moles;
+        }
+    }
+}