Using stream reader to catch values returned by sql statemtnt c#

Using stream reader to catch values returned by sql statemtnt c#

guys i have an SQL statement returning more than 1 value. I am trying to
use the StreamReader to get the values into an array as below
string sql = "select distinct COLUMN_NAME from
INFORMATION_SCHEMA.KEY_COLUMN_USAGE where TABLE_NAME=' " + table + "' and
CONSTRAINT_NAME like 'PK_%'";
SqlConnection conn2 = new
SqlConnection(cnstr.connectionString(cmbDatabase.Text));
SqlCommand cmd_server2 = new SqlCommand(sql);
cmd_server2.CommandType = CommandType.Text;
cmd_server2.Connection = conn2;
conn2.Open();
//reader_sql = new StreamReader();
SqlDataReader reader_sql = null;
string[] colName = new string[200];
reader_sql = cmd_server2.ExecuteReader();
while (reader_sql.Read());
for (int rr = 0; rr < 20; rr++)
{
colName[rr] = reader_sql["COLUMN_NAME"].ToString();
}
It is not working, what am I doing wrong guys ?