Creating A SQL MAX Command

Hello All,

 I'm currently in the process of developing a new PO system for work. What I need to accomplish is a SQL MAX command to find the largest PO number and then add 1 to that number. I'm then saving this in a session state so users can create multiple items for that same PO number. Here's what I have so far:

 

 1 protected void Page_Load(object sender, EventArgs e)
2 {
3 // connection string to your database
4 SqlConnection mySqlConnection = new SqlConnection("server=(local)\SQLEXPRESS;database=Purchasing;Integrated Security=SSPI;");
5
6 // create command object to execute query
7 SqlCommand mySqlCommand = mySqlConnection.CreateCommand();
8
9 // set command text to the INSERT sql query
10 mySqlCommand.CommandText = "SELECT MAX(PONumber)FROM ItemMaster;";
11
12 // open connection
13 mySqlConnection.Open();
14
15 // execute query
16
17 int newPO1 = (int) mySqlCommand.ExecuteScalar();
18 int newPO = newPO1 + 1;
19
20 // close connection
21 mySqlConnection.Close();
22
23 //Response.Write(newPO);
24 Session["newPO"] = newPO.ToString();
25
26 }


 

 I copied and modified the ExecuteScalar() command from another thread in another fourm, but continue to receive this error:

 

System.InvalidCastException: Specified cast is not valid.

Source Error:





Line 30: // execute query
Line 31:
Line 32: int newPO1 = (int) mySqlCommand.ExecuteScalar();
Line 33: int newPO = newPO1 + 1;
Line 34:

 

I'm not sure what i'm doing wrong, any help to point me in the right direction would be greatly appreciated.

 

Thank you in advance