Hello Xiaodong Liang, Thank you for the sample code for DeleteFaceFeatures. Well, we are working on a requirement in which a part file contains multiple shells (multiple solids). We want to get the mass properies of each shell independently. For example in a part, we have 4 shells, to get mass properties of 1st shell, we want to remove other 3 shells. This can be achieved using DeleteFaceFeatures. We have written the functionality as follows: 1. Collect the information for each shell - which other shell's faces should be deleted 2. The above information is stored in a collection 3. Then for each shell, other 3 shells are deleted and mass property is obtained. But many times we are getting error message which says: Run-time Error '-2147467259(80004005)': Method 'Add' of object 'DeleteFaceFeatures' failed The issue is definitely reproduced if we open the part file and do some operation like rotate and then run the program, otherwise it is intermittent issue. The error message comes while creating the DeleteFaceFeature for second shell Actually our program is in C++ and we always get error at following line: Result = pDeleteFaceFeatures->Add(pFaceCollection, Heal, &pDeleteFace); Result is always E_FAIL. The logic is exactly same as written in VBA. Please advise what could be the reason for the same. We could not attach the sample part file and it can be created by drawing 4 rectangles in a 2D sketch and extruding the same. Sub DeleteFaceFeatureFunction() Dim oDoc As PartDocument Set oDoc = ThisApplication.ActiveDocument 'oDoc.Activate Dim oFace As Face Dim TotalFaceShells As Integer 'Get total shell count TotalFaceShells = oDoc.ComponentDefinition.SurfaceBodies.Item(1).FaceShells.Count 'Get all the shells Dim oShells As FaceShells Set oShells = oDoc.ComponentDefinition.SurfaceBodies.Item(1).FaceShells Dim shellCnt As Integer shellCnt = 1 Dim iInnerShellCnt As Integer Dim oShellFaceColl As New Collection 'For each shell get which all other shells are to be removed While (shellCnt <= TotalFaceShells) Dim oFaceColl As FaceCollection Set oFaceColl = ThisApplication.TransientObjects.CreateFaceCollection iInnerShellCnt = 1 While (iInnerShellCnt <= TotalFaceShells) If (shellCnt = iInnerShellCnt) Then 'If both shells are same, skip Else Dim oFaceShell As FaceShell Set oFaceShell = oShells.Item(iInnerShellCnt) For Each oFace In oFaceShell.Faces Call oFaceColl.Add(oFace) Next End If iInnerShellCnt = iInnerShellCnt + 1 Wend Call oShellFaceColl.Add(oFaceColl, Str(shellCnt)) shellCnt = shellCnt + 1 Wend shellCnt = 1 'oDoc.Activate 'For each shell delete other shells and get the area While (shellCnt <= TotalFaceShells) Set oFaceColl = oShellFaceColl.Item(shellCnt) Dim oDeleteFace As DeleteFaceFeature Set oDeleteFace = oDoc.ComponentDefinition.Features.DeleteFaceFeatures.Add(oFaceColl, False) 'Get area Dim area As Double area = oDoc.ComponentDefinition.MassProperties.area Debug.Print area 'Delete the created feature oDeleteFace.Delete True, True, True shellCnt = shellCnt + 1 Wend End Sub Thanks & Regards, Mangesh