带字符串的自动增量ID

Question

I'm using Access 2000-2003 database for C#. I like to have my TypeID to have a unique id as CHHTP001 , CHHTP002 and etc, and display the id in TextBox before inserting new value in the database.

public void generateRateID()
{
     string id;
     con.Open();
     string rate = "SELECT MAX(TypeID) FROM tblRoomTypeRate";
     cmd = new OleDbCommand(rate, con);
     OleDbDataReader dr = cmd.ExecuteReader();
     if (dr.Read())
     {
          id = dr[0].ToString();
          id = id + 1;
          txtRateID.Text = "CHHRT" + id.PadLeft(3, '0');
     }
     con.Close();
}

The display in TextBox is CHHTP001 at first, then CHHTPCHHTP0011 . How can I make the CHHTPCHHTP0011 to CHHTP002 and so on?

Answer 1

Use Regex . This should works as you want:

id = dr[0].ToString();//CHHTP001 Or CHHTP111
id = Regex.Replace(id, "\\d+", m => (int.Parse(m.Value) + 1).ToString(new string('0', m.Value.Length)));
txtRateID.Text = id;//CHHTP002 Or CHHTP112

Answer 2

Here is some general guidelines.

You should create an int variable that records what should be the number. That way you can manage your id easily. When you want to increment your id, just increment the variable.

When you want to convert the id to a string, first call ToString and PadLeft . Next you just concatenate the string to "CHHTP"! Isn't that easy?

Answer 3

Try this:

{

 string id;

 string literal; // "CHHRT" or whatever;

 int sequence;

 con.Open();
 string rate = "SELECT MAX(TypeID) FROM tblRoomTypeRate";
 cmd = new OleDbCommand(rate, con);
 OleDbDataReader dr = cmd.ExecuteReader();
 if (dr.Read())
 {
     id = dr[0].ToString();
     sequence = int.Parse( new string( id.Where( char.IsDigit ).ToArray() ) );
     literal = new string( id.Where( char.IsLetter ).ToArray() );
     id = literal + ( sequence + 1 ).ToString( "000" );                
     txtRateID.Text = id;
 }
 con.Close();

}