【Revit 2025 API】 A Question about SetFormula

[yz8023yz]

When I execute the following code

FamilyManager manager = familyDoc.FamilyManager;

ForgeTypeId forgeTypeId_length = new ForgeTypeId("autodesk.spec.aec:length-2.0.0");
FamilyParameter parameter_qzh = manager.AddParameter("墙肢高度", GroupTypeId.Geometry, forgeTypeId_length, false);

I got this

But when I execute this one code:

manager.SetFormula(parameter_qzh, "侧墙高度 -底板厚度");

it will throw an error：There is no valid family type. at Autodesk.Revit.DB.FamilyManager.SetFormula(FamilyParameter familyParameter, String formula)

[TripleM-Dev.net]

Is there a Type active in the FamilyEditor, a parameter needs to be set while a type is set.

If no types are defined (the type box shows a grey inactive combobox) the values can't be set.

See remarks in: CurrentType  

I Think the UI can do this because it sets the type to the name of the family...

- Michel

[yz8023yz]

Hi, thanks for the reply, but I noticed that the type box is not showing the gray inactive combo box.

[yz8023yz · Accepted solution]

Add the following code for the creation parameter in the family document
// Checks to see if the current family type exists, and if not, creates the
FamilyType currentType = manager.CurrentType;
if (currentType == null)
{
currentType = manager.NewType("DefaultType");
}