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 !