ExecuteReader(); not work

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I want search database is user existing in the table.then i write this. but mark " SqlDataReader reder = cmd.ExecuteReader();" in yellow color and cant do my work?
is this problem abt" ExecuteReader()"???

help me ~~soon as possible~~

SqlConnection con = new SqlConnection("Data Source=thushan-pc;Initial Catalog=dvd;Integrated Security=True");
bool b=false;
SqlCommand cmd=new SqlCommand("select User_Name from users where=('"+txtop.Text+"')",con);
con.Open();

SqlDataReader reder = cmd.ExecuteReader();
if (reder.Read() == true)
b = true;
reder.Close();
cmd.Dispose();

con.Close();
if (b == true)
MessageBox.Show("User here");

Posted 1-Oct-10 7:56am

thushan0716

Updated 1-Oct-10 10:50am

Toli Cuturicu

v3

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OriginalGriff · Answer 1 · 2010-10-01T08:29:00

Firstly, don't do it like that - it leave you open to an SQL injection attack. Use parameterized queries instead (See SqlCommand.AddWithValue for details).

Secondly, the problem is your sql command. Try writing it out yourself assumeing txtop.Text is "John":

select User_Name from users where=('John')

Now try making it a legitimate Sql select statement:

SELECT User_Name FROM users WHERE User_Name='John'

(I have capitalised SQL syntax words to make it easier to decipher - worth doing as a general rule).

If you do this as a parameterized query, you won't need the quotes, either...

[edit]Finger trouble: there is no "Q" in "AddWithValue" - OriginalGriff[/edit]

Abhishek Sur · Answer 2 · 2010-10-01T09:41:00

If you need to just check the count why dont you use Count?

using(SqlConnection con = new SqlConnection("Data Source=thushan-pc;Initial Catalog=dvd;Integrated Security=True"))
{
bool b=false;
using(SqlCommand cmd=new SqlCommand("select Count(User_Name) from users where UserName='"+txtop.Text+"'",con))
{
  con.Open();

   SqlDataReader reder = cmd.ExecuteReader();
  if (reder.Read())
     if(Convert.ToInt32(dr[0]) == 1)
  {
     b = true;
     break;
  }
reder.Close();
cmd.Dispose();
}
con.Close();
if (b == true)
MessageBox.Show("User here");
}

It is a good practice to use Count rather than only to rely on reder.Read(). I hope this will help you. :rose:

ExecuteReader(); not work

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