This is how you add parameters to a standard CommandType.Text SQL call.
This should prevent sql injection attacks.
Using conSQL = New SqlConnection("CONNECTION STRING TO DATABASE")
Try
str = "SELECT * FROM TableName where customerid = @CustomerID and CartType = @CartType"
cmdSQL = New SqlCommand(str, conSQL)
cmdSQL.CommandType = CommandType.Text
cmdSQL.Parameters.AddWithValue("@CustomerID", CustomerID)
cmdSQL.Parameters.AddWithValue("@CartType", cartType)
cartcount = cmdSQL.ExecuteScalar()
Catch ex As Exception
cartcount = 0
End Try
End Using