Code working locally but not in Server, SQL and null string related

Question

Hello i have the following cs code

 SqlConnection con = new SqlConnection();
        SqlCommand com = new SqlCommand();
        String comando = "";
        con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["INBIOTECAConnectionString"].ToString());
        SqlDataReader leer = null;
        String diaUltimo = "";
        String fecha = DateTime.Now.ToString("dd/MM/yyyy");

        try
        {
            con.Open();
            comando = " SELECT TOP 1 hora FROM SI_RegEntrada  WHERE nombre = '" + name + "' and dia = '"+fecha+"' ORDER BY id DESC;";
            com = new SqlCommand(comando, con);
            leer = com.ExecuteReader();
            while (leer.Read())
            {
                diaUltimo = leer[0].ToString();
            }

            if (diaUltimo.Equals(""))
            {
                return false;
            }
            else
            {
                return true;
            }



        }
        catch (Exception ex)
        {
            return true;
        }
        finally
        {
            con.Close();
            con.Dispose();
            com.Dispose();
            com = null;
            con = null;
        }

It's supposed to be pretty simple, it's gonna check if there's an entry on the SI_RegEntrada table today (fecha) from any user (name).

SELECT TOP 1 hora FROM SI_RegEntrada  WHERE nombre = '" + name + "' and dia = '"+fecha+"' ORDER BY id DESC;

ok, so far so good, i proceed to read the results on the var diaUltimo.

On my local server, if there are no results (meaning that today, that user, hasn't interact with the system), diaUltimo will get the value of

 diaUltimo = ""

so I check for that in the if/else condition a return true or false. In the live server, it always falls on the catch clause, and return always true.

I was thinking that, maybe diaUltimo will get some kind of null value, or some sql error.

I cannot debug or interact with the live server.

well your query will return NULL, not an empty string if a user hasn't had any interaction, if that helps — S3S
– S3S, Commented Jul 6, 2017 at 21:02
in the catch, i tried to change the return of the catch to false, and it did it every time, so is 100% sure its falling in the catch — Erick Reyes
– Erick Reyes, Commented Jul 6, 2017 at 21:02
Its very important to know which line is raising exception. Even though you cannot debug but can you put some sort of logging to find at what line exception was raised. Probably connection is failing. — MKR
– MKR, Commented Jul 6, 2017 at 21:14

Travis Acton · Accepted Answer · 2017-07-06 22:06:08Z

2

Change the lines

if (diaUltimo.Equals(""))
{
  return false;
}
else
{
 return true;
}

to

if(!String.IsNullOrEmpty(diaUltimo))
{
 return true;
}
else
{
 return false;
}

It will work double duty in checking that you assigned value is neither null or empty

edited Jul 6, 2017 at 22:06

answered Jul 6, 2017 at 21:50

Travis Acton

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2 Comments

Erick Reyes Over a year ago

I was thinking something like that, even if in my local server, it works well, for now I'm going to try with something simpler that I had not thought of: if (leer.HasRows) { return true; } else { return false; }

S3S Over a year ago

Like I said @ErickReyes, your SQL returns NULL not an EMPTY string and NULL != anything including NULL. +1 Travis.

MKR · Accepted Answer · 2017-07-06 21:24:09Z

0

There is very high chance that con.Open() is raising exception. Nothing else looks problematic in your code.

answered Jul 6, 2017 at 21:24

MKR

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Comments

JasonInVegas · Accepted Answer · 2017-07-06 21:49:30Z

0

First, temporarily replace the string contents of comando to be a SQL command which is not dependent on your table or rows...something like:

static string commando = "Select to_char(sysdate) from dual";

This will do 2 things: it will test whether your connection object and SQLExecute both work as expected AND it will test the default format mask on date fields in your live database.

If you do not get any results then I would begin diagnosing the exception by not returning 'true' but instead raising an internal exception and passing the ex object contents out for your to inspect.

answered Jul 6, 2017 at 21:49

JasonInVegas

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