Linestring to use IPosition in Is_Closed

Author: matt-lethargic

src/GeoJSON.Net.Tests/Geometry/LineStringTests.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using GeoJSON.Net.Geometry;
 using Newtonsoft.Json;
@@ -39,6 +40,7 @@ public void Is_Not_Closed()
 
             Assert.IsFalse(lineString.IsClosed());
         }
+        
 
         [Test]
         public void Can_Serialize()
@@ -81,6 +83,19 @@ public void Can_Deserialize()
             Assert.AreEqual(expectedLineString.Coordinates[0].Longitude, actualLineString.Coordinates[0].Longitude);
         }
 
+        [Test]
+        public void Constructor_No_Coordinates_Throws_Exception()
+        {
+            var coordinates = new List<IPosition>();
+            Assert.Throws<ArgumentOutOfRangeException>(() => new LineString(coordinates));
+        }
+
+        [Test]
+        public void Constructor_Null_Coordinates_Throws_Exception()
+        {
+            Assert.Throws<ArgumentNullException>(() => new LineString(null));
+        }
+
         private LineString GetLineString(double offset = 0.0)
         {
             var coordinates = new List<IPosition>

src/GeoJSON.Net/Geometry/LineString.cs

@@ -65,18 +65,12 @@ public LineString(IEnumerable<IPosition> coordinates)
         /// </returns>
         public bool IsClosed()
         {
-            var firstCoordinate = Coordinates[0] as Position;
+            var firstCoordinate = Coordinates[0];
+            var lastCoordinate = Coordinates[Coordinates.Count - 1];
 
-            if (firstCoordinate != null)
-            {
-                var lastCoordinate = Coordinates[Coordinates.Count - 1] as Position;
-               
-                return firstCoordinate.Latitude == lastCoordinate.Latitude
-                       && firstCoordinate.Longitude == lastCoordinate.Longitude
-                       && firstCoordinate.Altitude == lastCoordinate.Altitude;
-            }
-
-            return Coordinates[0].Equals(Coordinates[Coordinates.Count - 1]);
+            return firstCoordinate.Longitude.Equals(lastCoordinate.Longitude)
+                   && firstCoordinate.Latitude.Equals(lastCoordinate.Latitude)
+                   && firstCoordinate.Altitude.Equals(lastCoordinate.Altitude);
         }
 
         /// <summary>