What you are describing is not concentricity. That is when arcs or circles share the same centerpoint.
If you want to check if an entity is inside a boundary you can use this example:
<CommandMethod("ChkInside", CommandFlags.Modal)> Public Shared Sub ChkInside()
Dim doc As Document = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument
Dim ed As Editor = doc.Editor
Dim db As Database = doc.Database
Dim peo As New PromptEntityOptions(vbLf & "Select circle: ")
peo.SetRejectMessage(vbLf & "Should be a circle!")
peo.AddAllowedClass(GetType(Circle), False)
Dim per As PromptEntityResult = ed.GetEntity(peo)
If per.Status <> PromptStatus.OK Then Return
Dim peo2 As New PromptEntityOptions(vbLf & "Select line: ")
peo2.SetRejectMessage(vbLf & "Should be a line!")
peo2.AddAllowedClass(GetType(Line), False)
Dim per2 As PromptEntityResult = ed.GetEntity(peo2)
If per2.Status <> PromptStatus.OK Then Return
Using trx As Transaction = db.TransactionManager.StartTransaction()
Dim Boundary As Curve = CType(trx.GetObject(per.ObjectId, OpenMode.ForRead), Curve)
Using trimmer As New Autodesk.AutoCAD.ExportLayout.Trimmer()
Dim EntityToCheck As Entity = CType(trx.GetObject(per2.ObjectId, OpenMode.ForWrite), Entity)
trimmer.Trim(EntityToCheck, Boundary)
If trimmer.EntityCompletelyInside Then
ed.WriteMessage(vbLf & "INSIDE")
Else
ed.WriteMessage(vbLf & "NOT INSIDE")
End If
End Using
End Using
End Sub
This is just a quick example to check if a selected line is inside a selected boundary (circle in this example).
It should be fairly easy to adapt this to check for a larger selection of entities.
