C#: Add some examples of using attributes on properties and indexers for use in external models.

csharp/ql/test/library-tests/dataflow/external-models/Sinks.cs

@@ -12,6 +12,12 @@ namespace My.Qltest
 
             object fieldWrite = new object();
             TaggedField = fieldWrite;
+
+            object propertyWrite = new object();
+            TaggedPropertySetter = propertyWrite;
+
+            object indexerWrite = new object();
+            this[0] = indexerWrite;
         }
 
         object SinkMethod()
@@ -34,7 +40,21 @@ namespace My.Qltest
 
         [SinkAttribute]
         object TaggedField;
+
+        [SinkPropertyAttribute]
+        object TaggedPropertySetter { get; set; }
+
+        [SinkIndexerAttribute]
+        object this[int index]
+        {
+            get { return null; }
+            set { }
+        }
     }
 
     class SinkAttribute : System.Attribute { }
-}
+
+    class SinkPropertyAttribute : System.Attribute { }
+
+    class SinkIndexerAttribute : System.Attribute { }
+}

csharp/ql/test/library-tests/dataflow/external-models/Sources.cs

@@ -18,14 +18,17 @@ namespace My.Qltest
             x = TaggedSrcField;
 
             x = SrcTwoArg("", "");
+
+            x = TaggedSrcPropertyGetter;
+            x = this[0];
         }
 
-        [SourceAttribute()]
+        [SourceAttribute]
         void Tagged1(object taggedMethodParam)
         {
         }
 
-        void Tagged2([SourceAttribute()] object taggedSrcParam)
+        void Tagged2([SourceAttribute] object taggedSrcParam)
         {
         }
 
@@ -49,14 +52,20 @@ namespace My.Qltest
 
         void SrcArg(object src) { }
 
-        [SourceAttribute()]
+        [SourceAttribute]
         object TaggedSrcMethod() { return null; }
 
-        [SourceAttribute()]
+        [SourceAttribute]
         object TaggedSrcField;
 
         object SrcTwoArg(string s1, string s2) { return null; }
+
+        [SourceAttribute]
+        object TaggedSrcPropertyGetter { get; }
+
+        [SourceAttribute]
+        object this[int i] => null;
     }
 
     class SourceAttribute : System.Attribute { }
-}
+}