Get the dimension of part

Not sure what are you trying to accomplish with this.

If you're trying to get the length of all the lines in the sketch "Esquisse1", use this:

'Open a part and select a sketch

Option Explicit

Sub main()

    Dim swApp As SldWorks.SldWorks

    Dim swModel As SldWorks.ModelDoc2

    Dim swSelMgr As SldWorks.SelectionMgr

    Dim swFeat As SldWorks.Feature

    Dim swSketch As SldWorks.Sketch

    Dim vSketchSegs As Variant

    Dim vSketchSeg As Variant

    Dim swSketchSeg As SldWorks.SketchSegment

    Dim boolstatus As Boolean

    Set swApp = Application.SldWorks

    Set swModel = swApp.ActiveDoc

    Set swSelMgr = swModel.SelectionManager

    'boolstatus = Part.Extension.SelectByID2("Esquisse1", "SKETCH", 0, 0, 0, False, 0, Nothing, 0)

    Set swFeat = swSelMgr.GetSelectedObject6(1, -1)

    Set swSketch = swFeat.GetSpecificFeature2

    vSketchSegs = swSketch.GetSketchSegments

    For Each vSketchSeg In vSketchSegs

        Set swSketchSeg = vSketchSeg

        If swSketchSeg.GetType <> swSketchSegments_e.swSketchTEXT Then

            MsgBox swSketchSeg.GetLength

        End If

    Next

End Sub

if you're trying to get the length of 1 selected line in the sketch "Esquisse1", use:

'Open a sketch and select a line

Option Explicit

Dim swApp As SldWorks.SldWorks

Dim Part As SldWorks.ModelDoc2

Dim SelectionManager As SldWorks.SelectionMgr

Dim SketchSegment As SldWorks.SketchSegment

Dim length As Double

Dim boolstatus As Boolean

Sub main()

Set swApp = Application.SldWorks

Set Part = swApp.ActiveDoc

'boolstatus = Part.Extension.SelectByID2("Line1", "SKETCHSEGMENT", 0, 0, 0, False, 0, Nothing, 0)

Set SelectionManager = Part.SelectionManager

Set SketchSegment = SelectionManager.GetSelectedObject6(1, -1)

Length = SketchSegment.GetLength

MsgBox (Length)

End Sub