Frequently Asked Questions

How To Do

ShowRubberBandEntities is a method of DXFReaderNETControl that displays a “rubber band” preview for a list of entities. In CAD/viewer terminology, a rubber band is a temporary, interactive drawing overlay used to preview something while the user is still interacting (e.g., dragging with the mouse), before you actually commit changes to the drawing/model. (dxfreader.net)

What it does

• It renders a preview of the provided entities.

• Optionally, it can preview them at a new position.

Signature (C#)

public void ShowRubberBandEntities(
    List<EntityObject> Entities,
    Vector2? Position = null
)

Parameters explained

Entities (required)

• Type: List<EntityObject>

• Meaning: the list of entities that should appear in the rubber-band preview. 

Typical content could be one or more geometric objects (lines, polylines, arcs, inserts, etc.) represented as EntityObject instances.

Position (optional)

• Type: Vector2? (nullable)

• Meaning: new position of entities (i.e., where the entities should be shown during the preview).

Because it’s nullable, you have two modes:

• Position == null: show the rubber band for the given entities “as is” (preview without relocating them).

• Position != null: show the same entities previewed at a new position, which is commonly used for “drag move” or “place object” interactions.

Typical interaction flow (how it’s used in an app)

A common usage pattern looks like this:

1. User starts an action (e.g., mouse down on a selection)

• Your app identifies which entities are being manipulated.

• You store them into a List<EntityObject>.

2. User moves the mouse

• You compute the target position in world coordinates (usually via a pixel→world conversion offered by the control).

• You call ShowRubberBandEntities(entities, currentPosition) repeatedly while the mouse moves.

• The control redraws the rubber-band overlay so the user sees the objects “following” the cursor.

3. User ends the action (mouse up)

• You commit the transformation (apply the move/placement to the actual entities in your model / DXF document).

• You typically trigger a refresh/regeneration of the main drawing view (depending on the control’s workflow), and stop showing the rubber band.

This method is about visual feedback: it is designed to show a temporary preview; the actual “real” geometry change (move/transform) is usually done by your code when the interaction is confirmed.

RubberBandType Enumeration

The enum values and their documented behavior are:

• Dashed (0)
  Draw rubber band dashed.

• Solid (1)
  Draw rubber band solid.

• CurrentColor (2)
  Draw rubber band solid using the current color.

• EntityColor (3)
  Draw rubber band solid using each entity’s own color.

• Dot (4)
  Draw rubber band dotted.

The purpose of this enum is to control how the rubber band looks, so you can choose:

• a clearly “temporary” appearance (dashed/dotted), or

• a more “realistic” preview matching either the control’s current drawing color or each entity’s color.