wpf填充datagridview方法

Question

public void ListTeacher()
        {
            this.datagridview2.AllowUserToAddRows = false;
            DataSet ds = new DataSet();
            string sql = string.Format("select tname from teacher");
            SqlDataAdapter adapter = new SqlDataAdapter(sql,DBHelper.connection);
            DBHelper.connection.Open();
            adapter.Fill(ds,"Teacher");
            datagridview2.DataSource = ds.Tables[0];
            DBHelper.connection.Close();
        }这个方法总是报出“未将对象引用到对象的实例”

Answer 1

怎么不是应该先打开Connection么？
出错应该是
datagridview2.DataSource = ds.Tables[0];
ds.Tables[0]有内容么？public void ListTeacher()
  {
  this.datagridview2.AllowUserToAddRows = false;
  DataSet ds = new DataSet();
  DBHelper.connection.Open(); // 这一句提前吧
  string sql = string.Format("select tname from teacher");
  SqlDataAdapter adapter = new SqlDataAdapter(sql,DBHelper.connection);
  adapter.Fill(ds,"Teacher");
  datagridview2.DataSource = ds.Tables[0];
  DBHelper.connection.Close();
  }