Tutorial 2: Parameters Deep Dive

Learn to read element parameters, understand storage types, and handle Revit's internal units.

Finished Script: 03_Tutorials/RevitAPI_Fundamentals/02_ParametersDeepDive.cs

🎯 What You'll Learn

• Accessing Built-in Parameters
• The four Parameter Storage Types
• Converting from internal units to display units

Understanding Parameters

Every Revit element has parameters - properties like Height, Width, Comments, etc. There are two ways to access them:

Built-in Parameters

Pre-defined by Revit, accessed via BuiltInParameter enum:

var param = element.get_Parameter(BuiltInParameter.WALL_USER_HEIGHT_PARAM);

Named Parameters

Custom or shared parameters, accessed by name:

var param = element.LookupParameter("My Custom Parameter");

Step 1: Check if Parameter Exists

Always check for null:

var param = wall.get_Parameter(BuiltInParameter.WALL_USER_HEIGHT_PARAM);

if (param == null)
{
    Println("Parameter not found on this element");
    return;
}

Step 2: Read Based on Storage Type

Parameters store values in one of four types:

StorageType	C# Type	Read Method
String	string	param.AsString()
Integer	int	param.AsInteger()
Double	double	param.AsDouble()
ElementId	ElementId	param.AsElementId()

string value = param.StorageType switch
{
    StorageType.String => param.AsString() ?? "(empty)",
    StorageType.Double => param.AsDouble().ToString("F2"),
    StorageType.Integer => param.AsInteger().ToString(),
    StorageType.ElementId => param.AsElementId().ToString(),
    _ => "Unknown type"
};

Step 3: Handle Units

Critical: Revit stores all lengths in feet internally!

double heightInFeet = param.AsDouble();

// Convert to meters
double heightInMeters = UnitUtils.ConvertFromInternalUnits(
    heightInFeet, 
    UnitTypeId.Meters
);

Println($"Height: {heightInMeters:F2} m");

Common unit conversions:

• UnitTypeId.Meters - Length in meters
• UnitTypeId.Millimeters - Length in millimeters
• UnitTypeId.SquareMeters - Area in m²
• UnitTypeId.CubicMeters - Volume in m³

Step 4: Common Built-in Parameters

// Wall parameters
BuiltInParameter.WALL_USER_HEIGHT_PARAM  // Unconnected Height
BuiltInParameter.CURVE_ELEM_LENGTH       // Length

// Room parameters
BuiltInParameter.ROOM_NAME
BuiltInParameter.ROOM_NUMBER
BuiltInParameter.ROOM_AREA

// Universal parameters
BuiltInParameter.ALL_MODEL_INSTANCE_COMMENTS
BuiltInParameter.ALL_MODEL_MARK

💡 Try This

1. Read and display the Area of all Rooms
2. Create a table showing Door widths and heights
3. Find all elements with empty Comments parameters

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Next: Tutorial 3: Conditional Logic →