ParameterValueSource.FromType made nullable (#1558)

Author: pawelbaran

Revit_Core_Engine/Compute/TryGetValueFromSource.cs

@@ -53,7 +53,7 @@ public static Output<bool, object> TryGetValueFromSource(this Element element, P
                 return null;
             }
 
-            if (valueSource.FromType)
+            if (valueSource.FromType == true)
             {
                 Element type = element.Document.GetElement(element.GetTypeId());
                 if (type != null)
@@ -66,6 +66,13 @@ public static Output<bool, object> TryGetValueFromSource(this Element element, P
             }
 
             Parameter param = element?.LookupParameter(valueSource.ParameterName);
+            if (param == null && valueSource.FromType == null)
+            {
+                param = element.Document.GetElement(element.GetTypeId())?.LookupParameter(valueSource.ParameterName);
+                if (param != null)
+                    BH.Engine.Base.Compute.RecordNote($"Parameter {valueSource.ParameterName} was not found in the instance of element {element.Id.IntegerValue}, but was found in the type.");
+            }
+
             if (param == null)
             {
                 BH.Engine.Base.Compute.RecordNote($"Element with id {element.Id} does not have a parameter named {valueSource.ParameterName}.");

Revit_oM/Parameters/ParameterValueSource.cs

@@ -35,8 +35,9 @@ public class ParameterValueSource : IValueSource
         [Description("Name of the parameter to extract the value from.")]
         public virtual string ParameterName { get; set; } = "";
 
-        [Description("If true, the value to be extracted from the underlying type, not the instance.")]
-        public virtual bool FromType { get; set; } = false;
+        [Description("If true, the value to be extracted from the underlying type, not the instance." +
+                     "\nIf set to null, first instance will be checked for the parameter with given name, and if not found then same will be done with its type.")]
+        public virtual bool? FromType { get; set; } = null;
 
         /***************************************************/
     }