Linear density enhancements (#1251)

Added operator overloads for all relations between LinearDensity, Mass and Length, with unit tests.

resolves #1250

Author: HakonJohannessen

UnitsNet.Tests/CustomCode/LinearDensityTests.cs

@@ -63,5 +63,12 @@ public void LinearDensityDividedByDensityEqualsArea()
             Area area = LinearDensity.FromGramsPerCentimeter(10) / Density.FromGramsPerCubicCentimeter(2);
             Assert.Equal(5, area.SquareCentimeters);
         }
+
+        [Fact]
+        public void LinearDensityTimesLengthEqualsMass()
+        {
+            Mass mass = LinearDensity.FromGramsPerCentimeter(10) * Length.FromCentimeters(2);
+            Assert.Equal(20, mass.Grams);
+        }
     }
 }

UnitsNet.Tests/CustomCode/MassTests.cs

@@ -118,6 +118,20 @@ public void MassTimesAccelerationEqualsForce()
             Assert.Equal(force, Force.FromNewtons(54));
         }
 
+        [Fact]
+        public void MassDividedByLengthEqualsLinearDensity()
+        {
+            LinearDensity linearDensity = Mass.FromKilograms(18) / Length.FromMeters(3);
+            Assert.Equal(linearDensity, LinearDensity.FromKilogramsPerMeter(6));
+        }
+
+        [Fact]
+        public void MassDividedByLinearDensityEqualsLength()
+        {
+            Length length = Mass.FromKilograms(18) / LinearDensity.FromKilogramsPerMeter(3);
+            Assert.Equal(length, Length.FromMeters(6));
+        }
+
         [Fact]
         public void NegativeMassToStonePoundsReturnsCorrectValues()
         {

UnitsNet/CustomCode/Quantities/LinearDensity.extra.cs

@@ -17,5 +17,11 @@ public partial struct LinearDensity
         {
             return Area.FromSquareMeters(linearDensity.KilogramsPerMeter / density.KilogramsPerCubicMeter);
         }
+
+        /// <summary>Get <see cref="Mass"/> from <see cref="LinearDensity"/> times <see cref="Length"/>.</summary>
+        public static Mass operator *(LinearDensity linearDensity, Length length)
+        {
+            return Mass.FromKilograms(linearDensity.KilogramsPerMeter * length.Meters);
+        }
     }
 }

UnitsNet/CustomCode/Quantities/Mass.extra.cs

@@ -99,6 +99,18 @@ public static Mass FromStonePounds(double stone, double pounds)
         {
             return Force.FromNewtons(mass.Kilograms*acceleration.MetersPerSecondSquared);
         }
+
+        /// <summary>Get <see cref="LinearDensity"/> from <see cref="Mass"/> times <see cref="Length"/>.</summary>
+        public static LinearDensity operator /(Mass mass, Length length)
+        {
+            return LinearDensity.FromKilogramsPerMeter(mass.Kilograms / length.Meters);
+        }
+
+        /// <summary>Get <see cref="Length"/> from <see cref="Mass"/> divided by <see cref="LinearDensity"/>.</summary>
+        public static Length operator /(Mass mass, LinearDensity linearDensity)
+        {
+            return Length.FromMeters(mass.Kilograms / linearDensity.KilogramsPerMeter);
+        }
     }
 
     /// <summary>