can you help me in data set?

your code seems true there is no error but if you get null dataset then check users table or conncetion string. and put your code in try catch block like....

class Serach
{
  conect co = new conect();
  public  DataSet ds = new DataSet();
  public DataSet   SearchKarmand(string serch)
  {
    try
    {
       SqlDataAdapter da = new SqlDataAdapter("select * from users", co.conn());
       da.Fill(ds);
    }
    catch(Exception ex)
    {
       MessageBox.Show("Error "+ex.Message);
       return null;
    }
    return ds;
  }
}