replace usage of string.Split(char[], int), not supported in full PCL profile (#119)

Test/Flurl.Test.Shared/CommonExtensionsTests.cs

@@ -101,5 +101,14 @@ namespace Flurl.Test
 			};
 			Assert.Throws<ArgumentException>(() => kv.ToKeyValuePairs().ToList());// need to force it to iterate for the exception to be thrown
 		}
+
+// todo: why can't netcore test app find SplitOnFirstOccurence? (making it public doesn't help)
+#if !NETCOREAPP1_0
+		[Test]
+		public void SplitOnFirstOccurence_works() {
+			var result = "hello/how/are/you".SplitOnFirstOccurence('/');
+			Assert.AreEqual(new[] { "hello", "how/are/you" }, result);
+		}
+#endif
 	}
 }

src/Flurl.Shared/Url.cs

@@ -42,9 +42,9 @@ namespace Flurl
 			if (baseUrl == null)
 				throw new ArgumentNullException(nameof(baseUrl));
 
-			var parts = baseUrl.Split(new[] { '#' }, 2);
+			var parts = baseUrl.SplitOnFirstOccurence('#');
 			Fragment = (parts.Length == 2) ? parts[1] : "";
-			parts = parts[0].Split(new[] { '?' }, 2);
+			parts = parts[0].SplitOnFirstOccurence('?');
 			Query = (parts.Length == 2) ? parts[1] : "";
 			Path = parts[0];
 		}
@@ -62,7 +62,7 @@ namespace Flurl
 
 			result.AddRange(
 				from p in query.Split('&')
-				let pair = p.Split(new[] { '=' }, 2)
+				let pair = p.SplitOnFirstOccurence('=')
 				let name = pair[0]
 				let value = (pair.Length == 1) ? "" : pair[1]
 				select new QueryParameter(name, value, true));

src/Flurl.Shared/Util/CommonExtensions.cs

@@ -48,6 +48,20 @@ namespace Flurl.Util
 			return obj.ToString();
 		}
 
+		/// <summary>
+		/// Needed because full PCL profile doesn't support Split(char[], int) (#119)
+		/// </summary>
+		internal static string[] SplitOnFirstOccurence(this string s, char separator) {
+			if (string.IsNullOrEmpty(s))
+				return new[] { s };
+
+			var i = s.IndexOf(separator);
+			if (i == -1)
+				return new[] { s };
+
+			return new[] { s.Substring(0, i), s.Substring(i + 1) };
+		}
+
 		private static IEnumerable<KeyValuePair<string, object>> StringToKV(string s) {
 			return Url.ParseQueryParams(s).Select(p => new KeyValuePair<string, object>(p.Name, p.Value));
 		}