Retrieving All Available Line Styles

I mentioned an AEC DevBlog post providing sample code showing how to retrieve all line styles through the CurveElement GetLineStyleIds property and mentioned that you can create a temporary curve element to invoke the property on in a separate transaction which is rolled back afterwards.

Actually, there is no need at all for all this rigmarole, as the following answer to a developer query shows:

Question: I need to retrieve all the available line styles in a project.

I did some research and found the abovementioned blog post requiring a dummy line to achieve that.

This seems to be inconsistent with obtaining other project data like Material and FillPattern instances.

You can easily make selections of all kinds, like these:

    .Where( c => c.GetType() == typeof(Material) )
    .Where( c => c.GetType() == typeof(FillPatternElement) )

I find it rather strange that you need a dummy line to obtain line styles.

Is there a better way, please?

Answer: While the Revit API does not provide a true 'Line style' element, the line styles are actually subcategories of the Lines category. Therefore, the FilteredElementCollector cannot easily be used for this in a single statement, like in your examples above.

It should be possible to retrieve the line styles without a line instance, though.

Here’s a macro that lists all subcategories of the Lines category:

  public void GetListOfLinestyles( Document doc )
    Category c = doc.Settings.Categories.get_Item(
      BuiltInCategory.OST_Lines );
    CategoryNameMap subcats = c.SubCategories;
    foreach( Category lineStyle in subcats )
      TaskDialog.Show( "Line style", string.Format(
        "Linestyle {0} id {1}", lineStyle.Name,
        lineStyle.Id.ToString() ) );

Note that some line styles like 'Room Boundary' cannot actually be assigned to arbitrary lines in the UI, but this should be good enough to find a usable one.

Once you have a collection of the line style subcategories of interest, you can create a filtered element collector retrieving all ElementType elements belonging to any one of them.