This .NET class wraps the AcDbAlignedDimension ObjectARX class. 

The AlignedDimension class is used to represent the dimension type that dimensions the distance between two points located anywhere in space. The dimension’s normal vector must be perpendicular to the line between the two points. The two selected points are also used as the definition points for the start of the two dimension extension lines.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.Entity
        Autodesk.AutoCAD.DatabaseServices.Dimension
            Autodesk.AutoCAD.DatabaseServices.AlignedDimension

Public Class AlignedDimension
Inherits Dimension

public class AlignedDimension : Dimension;

When a newly created dimension entity is first closed, an anonymous block will automatically be created for it to reference for display. The anonymous block is an BlockTableRecord that contains all the appropriate line, arc, arrowhead solids, text, and others, and with *D as the block name prefix. 

If the dimension has been set to use the text position value rather than the default text position (that is, Dimension.TextPosition has been set) and the DIMFIT system variable is not set to 4, then the text position will take precedence over the dimLine setting.

DBObject, Entity