Do not throw if assembly cannot be loaded (#29)

Author: SzymonPobiega

src/NServiceBus.FileBasedRouting.Tests/XmlRoutingFileTests.cs

@@ -120,6 +120,25 @@ public void It_provides_distinct_result_even_when_types_are_registered_multiple_
             CollectionAssert.AreEquivalent(new[] { typeof(A), typeof(B) }, configuration.Commands);
         }
 
+        [Test]
+        public void It_does_not_throw_if_assembly_cannot_be_found()
+        {
+            const string xml = @"
+ <endpoints>
+  <endpoint name=""EndpointName"">
+    <handles>
+      <commands assembly = ""FooBar"" />
+    </handles>
+  </endpoint>
+ </endpoints>
+ ";
+            var configurations = GetConfigurations(xml);
+
+            Assert.AreEqual(1, configurations.Length);
+            var configuration = configurations[0];
+            Assert.AreEqual("EndpointName", configuration.LogicalEndpointName);
+        }
+
 
         static EndpointRoutingConfiguration[] GetConfigurations(string xml)
         {

src/NServiceBus.FileBasedRouting/XmlRoutingFileParser.cs

@@ -82,7 +82,17 @@ static Type FindMessageType(string typeName)
         static IEnumerable<Type> SelectMessages(XElement commandsElement)
         {
             var assemblyName = commandsElement.Attribute("assembly").Value;
-            var assembly = Assembly.Load(assemblyName);
+            Assembly assembly;
+            try
+            {
+                assembly = Assembly.Load(assemblyName);
+            }
+            catch
+            {
+                logger.Warn($"Cannot add route for unknown assembly {assemblyName}.");
+                return Enumerable.Empty<Type>();
+            }
+            
             var exportedTypes = assembly.ExportedTypes;
             var @namespace = commandsElement.Attribute("namespace");
             if (@namespace == null)