SQL parameter either integer value or dbnull pass to query - vb.net

Question

Can't get my query to work. I want to pass either integer value or dbnull to my query but in that form is not working. Below my code.
Query:
Using cmd As New SqlCommand("SELECT COUNT(*) FROM tbSuSubSections_Sentences WHERE FK_Sentence_Id = #FK_Sentence_Id And FK_SubSection_Id = #FK_SubSection_Id And FK_SubSubKategorie_Id=#FK_SubSubKategorie_Id", con)
Parameter set up based on which one i need:
If _FK_SubSubKategorie_Id = 0 Then
cmd.Parameters.AddWithValue("#FK_SubSubKategorie_Id", DBNull.Value)
Else
cmd.Parameters.AddWithValue("#FK_SubSubKategorie_Id", _FK_SubSubKategorie_Id)
End If
if _FK_SubSubKategorie_Id is set to DBNull as shown my query should change a bit instead this part:
And FK_SubSubKategorie_Id=#FK_SubSubKategorie_Id", con)
to
And FK_SubSubKategorie_Id IS NULL", con)
What is the right way to do?
that's entire SQL function:
#Region "Check if connection already exist"
Public Function CheckIfConnectionAlreadyExist(_FK_Sentence_Id As Integer, _FK_SubSection_Id As Integer, _FK_SubSubKategorie_Id As Integer) As Boolean
Dim result As Boolean
Dim strcon = New AppSettingsReader().GetValue("ConnectionString", GetType(String)).ToString()
Using con As New SqlConnection(strcon)
Using cmd As New SqlCommand("SELECT COUNT(*) FROM tbSuSubSections_Sentences WHERE FK_Sentence_Id = #FK_Sentence_Id And FK_SubSection_Id = #FK_SubSection_Id And FK_SubSubKategorie_Id=#FK_SubSubKategorie_Id", con)
cmd.CommandType = CommandType.Text
cmd.Parameters.AddWithValue("#FK_Sentence_Id", _FK_Sentence_Id)
cmd.Parameters.AddWithValue("#FK_SubSection_Id", _FK_SubSection_Id)
If _FK_SubSubKategorie_Id = 0 Then
cmd.Parameters.AddWithValue("#FK_SubSubKategorie_Id", DBNull.Value)
Else
cmd.Parameters.AddWithValue("#FK_SubSubKategorie_Id", _FK_SubSubKategorie_Id)
End If
con.Open()
Dim o As Integer = cmd.ExecuteScalar()
If o > 0 Then
result = True
Else
result = False
End If
con.Close()
End Using
End Using
Return result
End Function
#End Region

Answer 1

Just create one query string which both conditions have in common and change it regarding _FK_SubSubKategorie_Id afterwards. Then create the command:
Dim qry as String = "SELECT COUNT(*) FROM tbSuSubSections_Sentences WHERE FK_Sentence_Id = #FK_Sentence_Id And FK_SubSection_Id = #FK_SubSection_Id And FK_SubSubKategorie_Id {0}"
If _FK_SubSubKategorie_Id = 0 Then
qry = string.Format(qry," IS NULL")
Else
qry = string.Format(qry, "=#FK_SubSubKategorie_Id"
End if
Using cmd As New SqlCommand(qry, con)
...