update C# ParamterToString to support array of object, add test case

samples/client/petstore/csharp/SwaggerClientTest/TestApiClient.cs

@@ -0,0 +1,26 @@
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using IO.Swagger.Client;
+
+namespace SwaggerClient.TestApiClient
+{
+	public class TestApiClient
+	{
+		[Test ()]
+		public void TestParameterToString ()
+		{	
+			ApiClient api = new ApiClient ();
+
+			// test array of string
+			List<string> statusList = new List<String>(new String[] {"available", "sold"});
+			Assert.AreEqual("available,sold", api.ParameterToString (statusList));
+
+			// test array of int
+			List<int> numList = new List<int>(new int[] {1, 37});
+			Assert.AreEqual("1,37", api.ParameterToString (numList));
+		}
+
+	}
+}
+