MySqlCommand().ExecuteReader().GetString() does not work

Question

I'm working with MySql in the C# programming language. I'm trying to get some data out of my database.

The fields are organized like this:

foo	baa
38737	22222

I need to get the value of foo if my hash is equal to baa

I tried this:

My code(not working)

MySqlConnection con = new 
    MySqlConnection("Server=localhost;Database=test;Uid=user;Pwd=pass;");
con.Open();
MySqlCommand cmd = new MySqlCommand();
cmd.CommandText = string.Format("SELECT * FROM info WHERE baa = '{0}'", Hash);
cmd.Connection = con;
MySqlDataReader reader = cmd.ExecuteReader();
String res = reader.GetString(0);

I'm getting the following error:

Invalid attempt to access a field before calling Read()

Can someone point out my error?

Should also point out that this method exposes you to SQL injection attacks. See little bobby tables about this. — Tejs
– Tejs, Commented Aug 15, 2011 at 3:15

BrokenGlass · Accepted Answer · 2011-08-15 03:03:18Z

12

You are missing a reader.Read() call:

 MySqlDataReader reader = cmd.ExecuteReader();
 while(reader.Read())
 {
     String res = reader.GetString(0); 
     //...
 }

answered Aug 15, 2011 at 3:03

BrokenGlass

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rsbarro · Accepted Answer · 2011-08-15 03:06:15Z

4

Try:

string res;
using(MySqlDataReader reader = cmd.ExecuteReader())
{
    if(reader.Read())
        res = reader.GetString(0);
    else
        res = "not found";
}

If you change the SQL command to return a single value, for example:

"SELECT foo FROM info WHERE baa = '{0}' LIMIT 1"

then you can also use cmd.ExecuteScalar():

string res = cmd.ExecuteScalar().ToString();

answered Aug 15, 2011 at 3:06

rsbarro

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