asp.net database connectivity

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please look at the following code:

C#

protected void Button2_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(constring);
        
        SqlCommand cmd = new SqlCommand();
       
        if (DropDownList3.SelectedItem.Text == "Economy")
        {
            seats = Convert.ToInt32(DropDownList1.SelectedItem.Text);

            cmd.Connection = con;
            con.Open();
            cmd.CommandText = "select easeats from flight where fno='" + fn + "'";
           int eds = Convert.ToInt32(cmd.ExecuteScalar());
            
           if (eds > seats)
            {
                Panel2.Visible = true;                //seats available
                cl = DropDownList3.SelectedItem.Text;  
                seat = seats.ToString();
                seats = eds;
            }

i am getting an error in the line
int eds = Convert.ToInt32(cmd.ExecuteScalar());
as:
Conversion failed when converting the varchar value to data type int.

Posted 22-Apr-12 3:53am

Member 8725176

Updated 22-Apr-12 3:55am

Mohamed Mitwalli

v2

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[no name] 22-Apr-12 10:03am

what is "fn" and what is "fno"?

Pramod Harithsa 23-Apr-12 9:22am

Use parameterized query instead of concatination, it may lead to SQL injection.

4 solutions

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OriginalGriff · Answer 1 · 2012-04-22T04:03:00

Look at the value in fn - it is not converting to a integer to compare against fno.

BTW: Don't do it that way. Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.

Sandeep Mewara · Answer 2 · 2012-04-23T03:06:00

Solution 2

Try:

C#

cmd.CommandText = "select easeats from flight where fno=" + fn ;

Based on the error it looks like 'fno' is a int type field and so the value passed should not be in single quotes.

Posted 23-Apr-12 3:06am

Sandeep Mewara

Pramod Harithsa · Answer 3 · 2012-04-23T03:25:00

Solution 3

cmd.CommandText = "select easeats from flight where fno='" + fn + "'";
int eds = Convert.ToInt32(cmd.ExecuteScalar());

variable easeats might have been declared as varchar so may be the cause for error.

Posted 23-Apr-12 3:25am

Pramod Harithsa

Updated 23-Apr-12 3:48am

v2

alok.mailbox · Answer 4 · 2012-04-23T03:40:00

Solution 4

ExecuteScalar returns first column of the first row in the result set returned by the query.

In your case it may be that column "easeats" data type is VARCHAR.

http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executescalar.aspx[^]

Posted 23-Apr-12 3:40am

alok.mailbox