C# ~ SQL query

an example query sql by SqlCommand, SqlDataReader, SqlConnection

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string sql = "select * from ggyy";

string connectString = ConfigurationManager.ConnectionStrings["ggyyConnectionString"].ConnectionString;

SqlConnection conn = new SqlConnection(connectString);

conn.Open();

SqlCommand cmd = new SqlCommand(sql, conn);

string qq = "";

try {

SqlDataReader r = cmd.ExecuteReader();

while (r.Read()) {

qq += (string)r["fieldName"].ToString();

}

r.Close();

} catch (Exception e) {

qq = e.Message;

}

conn.Close();

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first time i got message

ExecuteReader requires an open and available Connection. The connection's current state is closed.

because i didn't open the connection.....

conn.Open();