You are trying to execute the ExecuteScalar on your connection instead of your command. You need to change that line to be:
sqlCommand.ExecuteScalar()
To add to this, I would recommend that you change your naming conventions to be a bit clearer. For example, you have strSQLconnection representing the connection string while sqlConnection represents the SQL Connection object. That is confusing. It also doesn't follow good guidelines for naming conventions, which will cause you problems down the road. I would suggest something like connectionString for your connection string and sqlConnection for your SQL connection. That makes it a bit easier to understand what the job is for each.