C#: Add an ASP.NET flow source example when using the WebMethod attribute.

Author: michaelnebel

csharp/ql/test/library-tests/dataflow/flowsources/remote/RemoteFlowSource.cs

@@ -54,3 +54,32 @@ public static async void M3(System.Net.WebSockets.WebSocket webSocket)
         }
     }
 }
+
+namespace AspRemoteFlowSource
+{
+    using System.Web.Services;
+
+    public class MySubData
+    {
+        public string SubDataProp { get; set; }
+    }
+
+    public class MyData
+    {
+        public string DataField;
+        public string DataProp { get; set; }
+        public MySubData SubData { get; set; }
+    }
+
+    public class MyService
+    {
+        [WebMethod]
+        public void MyMethod(MyData data)
+        {
+            Use(data.DataProp);
+            Use(data.SubData.SubDataProp);
+        }
+
+        public static void Use(object o) { }
+    }
+}

csharp/ql/test/library-tests/dataflow/flowsources/remote/remoteFlowSource.expected

@@ -12,3 +12,4 @@ remoteFlowSources
 | RemoteFlowSource.cs:45:17:45:23 | access to parameter request | ASP.NET query string |
 | RemoteFlowSource.cs:45:17:45:42 | access to property RawUrl | ASP.NET unvalidated request data |
 | RemoteFlowSource.cs:52:55:52:61 | [post] access to local variable segment | external |
+| RemoteFlowSource.cs:77:37:77:40 | data | ASP.NET web service input |

csharp/ql/test/resources/stubs/System.Web.cs

@@ -454,3 +454,8 @@ public class SimpleTypeResolver : System.Web.Script.Serialization.JavaScriptType
         public SimpleTypeResolver() => throw null;
     }
 }
+
+namespace System.Web.Services
+{
+    public class WebMethodAttribute : Attribute { }
+}