Revit api. Retrieve all parameters and categories

[Nice3point]

Summary

I recently came across a problem from my business partner who wanted to get all the built-in Revit parameters to extract metadata such as data type, units, storage type, etc. As we know, this is not possible using Autodesk's public API.

Similar situation with categories, we can't get all the built-in categories, the only available way is to get them from the document settings, but it contains a very truncated list

Solution

We can use private code using reflection and pointers, we only need a document.
The point of the method is not to get them but create it.

Example code to get all parameters:

public static List<Parameter> GetBuiltinParameters(Document document)
{
    const BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly;
    
    var documentType = typeof(Document);
    var parameterType = typeof(Parameter);
    var assembly = Assembly.GetAssembly(parameterType);
    var aDocumentType = assembly.GetType("ADocument");
    var elementIdType = assembly.GetType("ElementId");
    var elementIdIdType = elementIdType.GetField("<alignment member>", bindingFlags)!;
    var getADocumentType = documentType.GetMethod("getADocument", bindingFlags)!;
    var parameterCtorType = parameterType.GetConstructor(bindingFlags, null, new[] {aDocumentType.MakePointerType(), elementIdType.MakePointerType()}, null)!;

    var builtinParameters = Enum.GetValues(typeof(BuiltInParameter));
    var parameters = new List<Parameter>(builtinParameters.Length);
    foreach (BuiltInParameter builtinParameter in builtinParameters)
    {
        var elementId = Activator.CreateInstance(elementIdType);
        elementIdIdType.SetValue(elementId, builtinParameter);

        var handle = GCHandle.Alloc(elementId);
        var elementIdPointer = GCHandle.ToIntPtr(handle);
        Marshal.StructureToPtr(elementId, elementIdPointer, true);

        var parameter = (Parameter) parameterCtorType.Invoke(new[] {getADocumentType.Invoke(document, null), elementIdPointer});
        parameters.Add(parameter);
        handle.Free();
    }

    return parameters;
}

Example code to get all categories:

public static List<Category> GetBuiltinCategories(Document document)
{
    const BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly;

    var documentType = typeof(Document);
    var categoryType = typeof(Category);
    var assembly = Assembly.GetAssembly(categoryType);
    var aDocumentType = assembly.GetType("ADocument");
    var elementIdType = assembly.GetType("ElementId");
    var elementIdIdType = elementIdType.GetField("<alignment member>", bindingFlags)!;
    var getADocumentType = documentType.GetMethod("getADocument", bindingFlags)!;
    var categoryCtorType = categoryType.GetConstructor(bindingFlags, null, new[] {aDocumentType.MakePointerType(), elementIdType.MakePointerType()}, null)!;

    var builtInCategories = Enum.GetValues(typeof(BuiltInCategory));
    var categories = new List<Category>(builtInCategories.Length);
    foreach (BuiltInCategory builtInCategory in builtInCategories)
    {
        var elementId = Activator.CreateInstance(elementIdType);
        elementIdIdType.SetValue(elementId, builtInCategory);

        var handle = GCHandle.Alloc(elementId);
        var elementIdPointer = GCHandle.ToIntPtr(handle);
        Marshal.StructureToPtr(elementId, elementIdPointer, true);

        var category = (Category) categoryCtorType.Invoke(new[] {getADocumentType.Invoke(document, null), elementIdPointer});
        categories.Add(category);
        handle.Free();
    }

    return categories;
}

Result

As a result, we have created all the parameters and all the categories of the entire Enum

Parameters:

Categories:

Limitations

Created parameters have no binding to the element, and consequently have no value, only metadata

[chuongmep]

@Nice3point it is awesome !

[chuongmep]

Hi @Nice3point , it look like not working in Revit 2025 ?

[Nice3point]

@chuongmep should work, RevitLookup gets the categories/parameters this way

[chuongmep]

I can confirm it working awesome, thank @Nice3point

[chuongmep]

I have some issue with duplidate parameter and I want to share for any have same issue :

 public static List<Autodesk.Revit.DB.Parameter> GetBuiltinParameters(Document document)
    {
        const BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly;

        var documentType = typeof(Document);
        var parameterType = typeof(Autodesk.Revit.DB.Parameter);
        var assembly = Assembly.GetAssembly(parameterType);
        var aDocumentType = assembly.GetType("ADocument");
        var elementIdType = assembly.GetType("ElementId");
        var elementIdIdType = elementIdType.GetField("<alignment member>", bindingFlags)!;
        var getADocumentType = documentType.GetMethod("getADocument", bindingFlags)!;
        var parameterCtorType = parameterType.GetConstructor(bindingFlags, null,
            new[] { aDocumentType.MakePointerType(), elementIdType.MakePointerType() }, null)!;

        var builtinParameters = Enum.GetValues(typeof(BuiltInParameter));
        var parameters = new List<Autodesk.Revit.DB.Parameter>(builtinParameters.Length);
        foreach (BuiltInParameter builtinParameter in builtinParameters)
        {
            var elementId = Activator.CreateInstance(elementIdType);
            elementIdIdType.SetValue(elementId, builtinParameter);

            var handle = GCHandle.Alloc(elementId);
            var elementIdPointer = GCHandle.ToIntPtr(handle);
            Marshal.StructureToPtr(elementId, elementIdPointer, true);

            var parameter = (Autodesk.Revit.DB.Parameter)parameterCtorType.Invoke(new[]
                { getADocumentType.Invoke(document, null), elementIdPointer });
            parameters.Add(parameter);
            handle.Free();
        }
        // unique by id and name 
        var uniqueParameters = parameters.GroupBy(p => new { p.Id, p.Definition?.Name })
            .Select(g => g.First())
            .ToList();
        return uniqueParameters;
    }

[jeremytammik]

just to clarify: these are the unique parameter names; the parameters themselves are not unique, of course, or, rather, several different parameters may share the identical display name.

[Nice3point]

Exactly! So removing duplicates by name may not be appropriate for all cases

[chuongmep]

I tried with code but look like it is double with identical display name as well

[Nice3point]

this is an API issue, creating a parameter by identical IDs

[jeremytammik]

this is a fundamental parameter design issue. the ongoing project to convert the revit parameter definitions to some kind of globally unique repository that can be shared across all BIMs world-wide should resolve this. i searched on the roadmap and did not find exactly what i was expecting, but this thing here comes close: https://portal.productboard.com/mhf8vce9ubfupbhkfomayvi1/c/61-parameters-classification-taxonomy

[Nice3point]

also, for user parameters https://portal.productboard.com/mhf8vce9ubfupbhkfomayvi1/c/14-parameter-duplication-management

[Nice3point]

I've handled this issue, RevitLookup will now display the name as in Enum. However, when going to "explore members" it will still be a one parameter as designed in the API

@chuongmep

The fix requires an additional call to GetNames, since in C# GetValues casts them to the same name

        var parameters = Enum.GetValues<BuiltInParameter>();
        var parameterNames = Enum.GetNames<BuiltInParameter>();
        var result = new List<UnitInfo>(parameters.Length);
        for (var i = 0; i < parameters.Length; i++)
        {
            ...
            var parameter = parameters[i];
            var name = parameterNames[i],
        }

[chuongmep]

That awesome, now I can see more clearly, Thanks @Nice3point