Index: binary-improvements2/MapRendering/Web/API/AbsRestApi.cs
===================================================================
--- binary-improvements2/MapRendering/Web/API/AbsRestApi.cs	(revision 388)
+++ binary-improvements2/MapRendering/Web/API/AbsRestApi.cs	(revision 389)
@@ -105,4 +105,23 @@
 		}
 
+		protected bool TryGetJsonField (JSONObject _body, string _fieldName, out int _value) {
+			_value = default;
+			
+			if (!_body.TryGetValue (_fieldName, out JSONNode fieldNode)) {
+				return false;
+			}
+
+			if (!(fieldNode is JSONValue valueField)) {
+				return false;
+			}
+
+			try {
+				_value = valueField.AsInt;
+				return true;
+			} catch (Exception) {
+				return false;
+			}
+		}
+
 		protected abstract void HandleRestGet (RequestContext _context);