Add alternative GetExtension() extension equivalent to Path.GetExtension()

Author: mythz

src/ServiceStack.Text/StringExtensions.cs

@@ -381,7 +381,8 @@ public static string[] SplitOnLast(this string strVal, string needle)
 
         public static string WithoutExtension(this string filePath)
         {
-            if (String.IsNullOrEmpty(filePath)) return null;
+            if (string.IsNullOrEmpty(filePath)) 
+                return null;
 
             var extPos = filePath.LastIndexOf('.');
             if (extPos == -1) return filePath;
@@ -390,6 +391,15 @@ public static string WithoutExtension(this string filePath)
             return extPos > dirPos ? filePath.Substring(0, extPos) : filePath;
         }
 
+        public static string GetExtension(this string filePath)
+        {
+            if (string.IsNullOrEmpty(filePath)) 
+                return null;
+
+            var extPos = filePath.LastIndexOf('.');
+            return extPos == -1 ? string.Empty : filePath.Substring(extPos);
+        }
+
         static readonly char[] DirSeps = new[] { '\\', '/' };
 
         public static string ParentDirectory(this string filePath)

tests/ServiceStack.Text.Tests/StringExtensionsTests.cs

@@ -82,6 +82,19 @@ public void Does_not_alter_filepath_without_extension()
             Assert.That("path/to/file.ext".WithoutExtension(), Is.EqualTo("path/to/file"));
         }
 
+        [TestCase(null, null)]
+        [TestCase("/", "")]
+        [TestCase("/a", "")]
+        [TestCase("/a.b", ".b")]
+        [TestCase("/a.b.c", ".c")]
+        [TestCase("/{a.b}.c", ".c")]
+        [TestCase("/:=#%$@{a.b}.c", ".c")]
+        public void Does_get_Path_extension(string actual, string expected)
+        {
+            Assert.That(actual.GetExtension(), Is.EqualTo(Path.GetExtension(actual)));
+            Assert.That(actual.GetExtension(), Is.EqualTo(expected));
+        }
+
         //         0         1
         //         01234567890123456789
         [TestCase("text with /* and <!--", "<!--", "/*", 10)]