feat(MultiAddress): try to create or return null

src/MultiAddress.cs

@@ -24,7 +24,7 @@ namespace Ipfs
     ///   A multi address is considered immutablle and value type equality is implemented.
     ///   </para>
     /// </remarks>
-    /// <seealso href="https://github.com/jbenet/multiaddr"/>
+    /// <seealso href="https://github.com/multiformats/multiaddr"/>
     public class MultiAddress : IEquatable<MultiAddress>
     {
         /// <summary>
@@ -357,7 +357,27 @@ static public implicit operator MultiAddress(string s)
             return new MultiAddress(s);
         }
 
-
+        /// <summary>
+        ///   Try to create a <see cref="MultiAddress"/> from the specified
+        ///   string.
+        /// </summary>
+        /// <param name="s">
+        ///   The string representation of a multi address, such as "/ip4/1270.0.01/tcp/5001".
+        /// </param>
+        /// <returns>
+        ///   <b>null</b> if the string cannot be parsed; otherwise a <see cref="MultiAddress"/>.
+        /// </returns>
+        public static MultiAddress TryCreate(string s)
+        {
+            try
+            {
+                return new MultiAddress(s);
+            }
+            catch
+            {
+                return null;
+            }
+        }
 
     }
 

src/NetworkProtocol.cs

@@ -13,6 +13,9 @@ namespace Ipfs
     /// <summary>
     ///   Metadata on an IPFS network address protocol.
     /// </summary>
+    /// <remarks>
+    ///   Protocols are defined at <see href="https://github.com/multiformats/multiaddr/blob/master/protocols.csv"/>.
+    /// </remarks>
     /// <seealso cref="MultiAddress"/>
     public abstract class NetworkProtocol
     {

test/MultiAddressTest.cs

@@ -297,6 +297,16 @@ public void Ipv6ScopeId_Ignored()
             Assert.AreEqual(ma2, ma1);
             Assert.AreEqual(ma2.ToString(), ma1.ToString());
         }
+
+        [TestMethod]
+        public void TryCreate()
+        {
+            Assert.IsNotNull(MultiAddress.TryCreate("/ip4/1.2.3.4/tcp/80"));
+            Assert.IsNull(MultiAddress.TryCreate(null));
+            Assert.IsNull(MultiAddress.TryCreate(" "));
+            Assert.IsNull(MultiAddress.TryCreate("/tcp/alpha")); // bad port
+            Assert.IsNull(MultiAddress.TryCreate("/foobar")); // bad protocol
+        }
     }
 }