ElementParameterFilter: Using FilterDoubleRule to Filter Element Parameters in VB.NET

Let’s look at how to use the FilterDoubleRule filter rule to filter number (double) type element parameters in VB.NET in this post. Supposing we’d like to find all walls with length more than ten feet, what shall we do?

The following code does so in VB.NET:

    Public Shared Function GetWallsLongerThan(ByVal doc As RvtDocument, ByVal w As Double, ByVal tolerance As Double) As ICollection(Of Autodesk.Revit.DB.ElementId)
        Dim provider As New Autodesk.Revit.DB.ParameterValueProvider(New Autodesk.Revit.DB.ElementId(CInt(BuiltInParameter.CURVE_ELEM_LENGTH)))
        Dim rule As New Autodesk.Revit.DB.FilterDoubleRule(provider, New Autodesk.Revit.DB.FilterNumericGreater(), w, tolerance)
        Dim filter As New Autodesk.Revit.DB.ElementParameterFilter(rule)

        Return (New Autodesk.Revit.DB.FilteredElementCollector(doc)).OfClass(GetType(Wall)).WherePasses(filter).ToElementIds()
End Function

 

A few highlights about the code:

• An ElementParameterFilter needs a filter rule, the FilterDoubleRule in this case.
• The FilterDoubleRule needs a parameter value provider (ParameterValueProvider) and a filter rule evaluator (FilterNumericRuleEvaluator), specifically the FilterNumericGreater here.
• The FilterDoubleRule also needs a value and a tolerance which are straightforward.
• The ParameterValueProvider needs an argument of parameter, as the wall length parameter BuiltInParameter.CURVE_ELEM_LENGTH in this case.
• The parameter is represented by an ElementId, which is the enumerator numeric value for BuiltInParameter types.
• A fast filter, ElementClassFilter, represented by its shortcut method (OfClass), is also used to narrow down the FilteredElementCollector first. It not only speeds up the search but also makes sure only walls are returned.

Curious people may ask: how did you figure out the CURVE_ELEM_LENGTH value of the BuiltInParameter enumerator is the right one to use as its name does not have anything to do with walls?

Good question! Though we still have to make some guess and do some experiment most of times to sort things like this out, a few RevitAddinCoder coders can help make the task a lot easier:

• Parameter Infoer Coder
• Parameter Categorizer Coder
• Parameter Retriever Coder

To use the method is very straightforward. Here is some test code in VB.NET:

…
Dim ids As ICollection(Of Autodesk.Revit.DB.ElementId) = GetWallsLongerThan(CachedDoc, 10, 0.0001)
TaskDialog.Show("ElementParameterFilter Test", String.Format("There are {0} walls longer than 10 feet.", ids.Count))
…

ElementParameterFilter Creator of RevitAddinCoder can create the code automatically in no time.