# Add Equation to selected part

**Yannick Proulx**Jul 11, 2016 3:12 PM

Hi Guys,

I'm trying to add an equation to a part.

If I run my code when ModelDoc is swapp.activeDoc then everything work fine, my equations are added without any problem.

If I try to add my equation from an assembly through the selectionManager it's not working.

I get my modelDoc in an assembly through this way : swcomp2 = swSelMgr.GetSelectedObjectsComponent2(i)

then convert to modelDoc2 by modelDoc = swcomp2.getmodeldoc2

i get the swEquationMgr.GetCount to work so the equationMgr is correctly connected.

but when i Try to add the equation I get -1 which mean equation was not added...

is it possible that you cannot add an equation from else where that the activeDoc??

thanks for your time

Yannick

@

** Function link_equation(modeldoc As SldWorks.ModelDoc2, dimensionName As String, propertyName As String) As Boolean**

** Debug.Print(modeldoc.GetPathName)**

** Dim swEquationMgr As SldWorks.EquationMgr = modeldoc.GetEquationMgr**

** Dim EquationStr As String = """" & dimensionName & """ = """ & propertyName & """"**

** If swEquationMgr Is Nothing Then**

** MsgBox("impossible d'atteindre le EquationMgr de la pièce " & modeldoc.GetPathName)**

** Return False**

** End If**

** Dim equationResult As Integer = 0**

** **

** Dim I As Integer**

** Debug.Print("Equation Count : " & swEquationMgr.GetCount) '<------------------ work fine here I get the Equation count**

** For i = 0 To swEquationMgr.GetCount - 1**

** If UCase(swEquationMgr.Equation(I)) = UCase(EquationStr) Then**

** Return True 'equation already exist**

** End If**

** Next**

** **

** Debug.Print(EquationStr)**

** If swEquationMgr.GetCount = 0 Then**

** If swEquationMgr.Add2(0, EquationStr, False) = -1 Then '<-------------------return 0 (ok) when modelDoc = activedoc and return -1 in assy**

** Debug.Print("equation not added")**

** Return False**

** End If**

** Else**

** If swEquationMgr.Add2(-1, EquationStr, False) = -1 Then**

** Debug.Print("equation not added")**

** Return False**

** End If**

** End If**

** Return True**

** End Function**