Document Properties

(It gets information about custom properties) Dim oPropName As Object = typeDocProperties.InvokeMember("Item", Reflection.BindingFlags.Default Or Reflection.BindingFlags.GetProperty, Nothing, objDocumentProperties, New Object() {sPropertyName})
Dim oPropNameType As Type = oPropName.GetType
Dim val As String = oPropNameType.InvokeMember("Value", Reflection.BindingFlags.Default Or Reflection.BindingFlags.GetProperty, Nothing, oPropName, New Object() {}).ToString Return val

a strange error upgraded to Win 7 Unable to cast COM object of type 'System.__ComObject' to interface type 'Microsoft.Office.Core.DocumentProperties'.
This operation failed because the QueryInterface call on the COM component for the interface with IID '{2DF8D04D-5BFA-101B-BDE5-00AA0044DE52}' failed due to the following error:
No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

It looks like that the method doesn't work in Win 7 anymore BUT just in some specific condition (It seems it has problem when a document is being opened, otherwise it's to be working fine)

I changed the code to use 'normal' approach and it seems to be working fine.

Dim properties As Microsoft.Office.Core.DocumentProperties
properties = CType(objDocument.CustomDocumentProperties, Office.DocumentProperties)

Dim prop = properties.Cast(Of Office.DocumentProperty)().FirstOrDefault(Function(x) x.Name.ToLower.Equals(sPropertyName.ToLower))
If prop Is Nothing Then Return String.Empty Return prop.Value

    Public Class CustomDocProperties 

        ' Note: Object type is used instead of Office.DocumentProperties to avoid a type conversion error
        Private CustomDocProps As Object 

        ' DocProperty code using Object
        Private ReadOnly Property DocProperty(ByVal Name As String) As Object 
            <DebuggerStepThrough()> _ 
            Get 
                Try 
                    ' Note: This is significantly faster than looping through the properties
                    Return CustomDocProps(Name.ToString) 
                Catch ex As Exception 
                    Return Nothing 
                End Try 
            End Get 
        End Property 

        Property Value(ByVal Name As EraCustomPropertyName) As Object 
            Get 
                Dim docProp As Object = DocProperty(Name) 
                If docProp IsNot Nothing Then 
                    Return docProp.Value 
                Else 
                    Return Nothing 
                End If 
            End Get 
            Set(ByVal value As Object) 
                Dim docProp As Object = DocProperty(Name) 
                If docProp IsNot Nothing Then 
                    docProp.Value = value                       ' set value  
                Else 
                    Add(Name, value)                     ' add new prop and set value  
                End If 
            End Set 
        End Property 

        Private Function Add(ByVal Name As String, ByVal Value As Object) As Object 
            If TypeOf Value Is Integer OrElse TypeOf Value Is Double Then 
                ' Numeric
                Return CustomDocProps.Add(Name.ToString, False, Core.MsoDocProperties.msoPropertyTypeNumber, Value) 
            Else 
                ' String
                Return CustomDocProps.Add(Name.ToString, False, Core.MsoDocProperties.msoPropertyTypeString, Value) 
            End If 
        End Function 

        Sub Delete(Name As String) 
            Dim docProp As Object = DocProperty(Name) 
            If docProp IsNot Nothing Then 
                docProp.delete() 
            End If 
        End Sub 

        Public Sub New(ByVal WordDoc As Word.Document, Optional ByVal TemplateProperty As Boolean = False) 
            If TemplateProperty Then 
                CustomDocProps = WordDoc.AttachedTemplate.CustomDocumentProperties 
            Else 
                CustomDocProps = WordDoc.CustomDocumentProperties 
            End If 
        End Sub 

    End Class