Mapping ParameterType to StorageType and Vise Using VB.NET

The Revit API provides two ways to categorize Parameter instances regarding data types, ParameterType and StorageType.  The StorageType enumeration only has five values:

 None
 Integer
 Double
 String
 ElementId
 
This type seems to be specifically for programmers. The None is apparently to indicate that the associated Parameter does not really have a meaningful data type. The Integer, Double and String are clear and easy for programmers to understand since every programming language has these data types. The ElementId is very Revit API particular but it is not something hard to understand as it’s widely used in the API and almost everything needs the id to identify itself in a Revit session.
The ParameterType is much more complex, has a lot more values, and is hard to understand sometimes. Only a handful is appended here for reference:

Invalid
Integer
Number
Length
Area
Volume
Angle
URL
Material
YesNo
Force
…

It provides a value, Invalid, which looks similar to the None in the StorageType, to indicate some Parameter does not really carry any meaningful ParameterType information. What are other values about then and do they always have a corresponding StorageType value?

The answer to the latter is apparently YES as each Parameter has both a StorageType and a ParameterType. As far as the first question is concerned, the enumeration value itself is pretty explanatory, e.g. Length representing some linear measurement, YesNo meaning a Boolean value, Material indicating a material reference, etc. In addition, obviously, each StorageType value can map to multiple ParameterType values, but it is not obvious in the API or the Revit itself which StorageType value maps exactly to what ParameterType values.

Let’s work out some VB.NET code here to sort it out in some degree.

Dim allElements As List(Of Autodesk.Revit.DB.Element) = ElementFinder.FindAllElements(CachedDoc)
Dim dictStorageTypeList As New Dictionary(Of StorageType, List(Of ParameterType))()
For Each e As Autodesk.Revit.DB.Element In allElements
    For Each p As Parameter In e.Parameters
        If Not dictStorageTypeList.ContainsKey(p.StorageType) Then
            dictStorageTypeList.Add(p.StorageType, New List(Of ParameterType)())
        End If
        If Not dictStorageTypeList(p.StorageType).Contains(p.Definition.ParameterType) Then
            dictStorageTypeList(p.StorageType).Add(p.Definition.ParameterType)
        End If
    Next
Next

Using sw As New StreamWriter("c:\ParameterTypeToStorageTypeMap.txt")
    For Each kvp As KeyValuePair(Of StorageType, List(Of ParameterType)) In dictStorageTypeList
        sw.WriteLine(kvp.Key)
        For Each pt As ParameterType In kvp.Value
            sw.WriteLine(String.Format(vbTab & "{0}", pt))
        Next
    Next
End Using

The complete code for the ElementFinder.FindAllElements help method is appended below:

Public Class ElementFinder
    Public Shared Function FindAllElements(ByVal doc As RvtDocument) As List(Of Autodesk.Revit.DB.Element)
        Dim list As New List(Of Autodesk.Revit.DB.Element)()

        Dim finalCollector As New Autodesk.Revit.DB.FilteredElementCollector(doc)

        Dim filter1 As New Autodesk.Revit.DB.ElementIsElementTypeFilter(False)
        finalCollector.WherePasses(filter1)
        Dim filter2 As New Autodesk.Revit.DB.ElementIsElementTypeFilter(True)
        finalCollector.UnionWith((New Autodesk.Revit.DB.FilteredElementCollector(doc)).WherePasses(filter2))

        list = finalCollector.ToElements()

        Return list
    End Function
End Class

By the way, it was created in a second by Element Finder of RevitAddinWizard.

The content of the file ParameterTypeToStorageTypeMap.txt may look like the following depending on what model the code will be tried on (bigger models with more parameters and more varieties will yield more comprehensive results):

Integer
            Invalid
            YesNo
            Integer
Double
            Number
            105
            Length
            Currency
            Angle
            ElectricalPotential
            TemperalExp
            Stress
            UnitWeight
            Area
            Volume
            Slope
            106
            PipingRoughness
            HVACAreaDividedByHeatingLoad
            HVACCoolingLoadDividedByArea
            HVACCoolingLoad
            HVACHeatingLoadDividedByArea
            HVACAirflow
            HVACAirflowDensity
            HVACHeatingLoad
            HVACAreaDividedByCoolingLoad
            HVACFactor
            ElectricalPowerDensity
            HVACHeatGain
            HVACTemperature
ElementId
            Invalid
            Text
            Material
            FamilyType
None
            Invalid
String
            Text
            URL
            Invalid

One odd thing as can be noticed is that a Parameter can have a good StorageType such as ElementId and String but a bad ParameterType (Invalid) at the same time. And keen readers may have noticed those 105 and 106 stuffs and wondered what they are really about. Frankly, I have been wondering too!

Parameter Filter of RevitAddinWizard can create parameter type filters in C# or VB.NET based on their StorageType or ParameterType or both plus some other criteria if necessary.