Generate autoincrement in c #

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Generate autoincrement in c #

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#2 by (0 votes)

1

I have a form in ASP.NET where I want to increase the Id in a textbox and show it in the text box, every time the user clicks on a button, it has to be updated.

Do this code but it does not work for me, it does not show the Folio in the text box

  private void Id()
    {
   SqlConnection conn = new SqlConnection();
        conn = new SqlConnection(this.conexion);
        conn.Open();
        SqlCommand cmd = new SqlCommand();
        try
        {
            cmd.CommandText = "select max(Folio) from Datos;";
            int valor = int.Parse(cmd.ExecuteScalar().ToString()) + 1;
            txtfolio.Text = Convert.ToString(valor);
        }
        catch(System.Exception ex)
        {

        }
 }

The method I added it in the High button:

      protected void Alta_Click(object sender, EventArgs e)
    {
      Id();
  }

c# asp.net

asked by KlonDTS 20.02.2017 в 19:13

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2 answers

0

Try an isnull:

select isnull(max(Folio), 0) from Datos;

I think that can work for you

answered by 20.02.2017 в 19:22

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score 0 · Accepted Answer

If you do not have any rows you will return null, your program fails on the line where you convert "null" to int, that conversion can not be done, I recommend you change your query for something like this:

select case when max(Folio) is null then 0 else max(Folio) end from Datos

Thus, from the query you will return 0 when you have no records and avoid the problem of null

Edit:

I did not realize you had not assigned the connection to SqlCommand, add this:

cmd.Connection = conn;

Just before calling ExecuteScalar.