Assign null value to a decimal field in SQL - sql

Question

I want to assign null value in a field in SQL 2014 which has a data type, decimal. I tried to use theses codes but I didn't get the way I wanted (providing that other fieldnames and values are present.)
query = "INSERT INTO DBNAME.TLTRPRGP(DECIMALVAL) VALUES(#DECIMALVAL)"
params = New String() {"BLGSCD"}
values = New String() {Nothing}
SaveUpdateDelete(query, params, values)
query = "INSERT INTO DBNAME.TLTRPRGP(DECIMALVAL) VALUES(#DECIMALVAL)"
params = New String() {"BLGSCD"}
values = New String() {DbNull.Value}
SaveUpdateDelete(query, params, values)
query = "INSERT INTO DBNAME.TLTRPRGP(DECIMALVAL) VALUES(#DECIMALVAL)"
params = New String() {"BLGSCD"}
values = New String() {VbNull}
SaveUpdateDelete(query, params, values)
Private Sub SaveUpdateDelete(ByVal sql As String, ByVal parameters() As String, ByVal Values() As String)
If con.State = ConnectionState.Open Then
con.Close()
End If
con.Open()
Dim command As New SqlCommand
command = New SqlCommand(sql, con)
For i = 0 To parameters.Count - 1
command.Parameters.AddWithValue("#" & parameters(i).ToString, Values(i))
Next
command.CommandText = sql
command.ExecuteNonQuery()
con.Close()
End Sub
The first code returns 0. The second returns syntax error saying "Value System.DbNull.Value cannot be converted to String". The third code returns 1. All these codes failed to return the right value which is suppose to be NULL or EMPTY. What else is there to try?

Answer 1

the issue is with the datatype of the values: you constrain it to be a string but there are values that cannot be converted to strings (eg: DBNull.Value).
the solution is to use the generic object as the datatype for the parameters passed to the function SaveUpdateDelete.