c sharp database connection problem

Please use this ..

private void button5_Click(object sender, EventArgs e)
        {
            string str = @"Data Source=J:\BerendinaSW\Payment20150408\Payment2015\Social.sdf;Persist Security Info=True";
 
            SqlConnection con = new SqlConnection(str);
           try{
            con.Open();
           }
            catch(Exception ){
 
                MessageBox.Show("cannot connect");
            }
           SqlCommand cm = new SqlCommand("SELECT * FROM [admin]",con);
           
           SqlDataReader reader = null;
           con.Open();
           reader = cm.ExecuteReader(); 
           con.Close();
           while (reader.Read())
           {
               if (textBox1.Text ==(reader["username"].ToString())  && textBox2.Text == (reader["password"].ToString()))
               {
                   label8.Visible = true;
               }
               else
               {
                   label9.Visible = true;
                   textBox1.Text = "";
                   textBox2.Text = "";
               }
           }
        }

Thanks
AARIF SHAIKH

private void button5_Click(object sender, EventArgs e)
{
string str = @"Data Source=J:\BerendinaSW\Payment20150408\Payment2015\Social.sdf;Persist Security Info=True";

SqlConnection con = new SqlConnection(str);
try{

if(con.State==ConnectionState.Open)
con.Close();
con.Open();
}
catch(Exception ){

MessageBox.Show("cannot connect");
}
SqlCommand cm = new SqlCommand("SELECT * FROM [admin]",con);
cm.Connection = con;
SqlDataReader reader = null;
reader = cm.ExecuteReader(); // error showing in here it is mentioning connection closed
while (reader.Read())
{
if (textBox1.Text ==(reader["username"].ToString()) && textBox2.Text == (reader["password"].ToString()))
{
label8.Visible = true;
}
else
{
label9.Visible = true;
textBox1.Text = "";
textBox2.Text = "";
}
}
}