ExecuteReader: CommandText 属性尚未初始化
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Student
{
  public partial class RPT : Form
  {
  public RPT()
  {
  InitializeComponent();
  }
  private string Rptstrconn;
  private SqlConnection sqlrptconn;
  private SqlDataAdapter sqlrptda;
  private string Rptconnstr="Data Source=WWW-F9EEA54BDCA;Initial Catalog=STUDENT;User ID=sa;Pwd=jxlsqd;Integrated Security=False";
  private SqlCommandBuilder sqlrptcomm;
  private DataSet Rptset = new DataSet();

  private void button1_Click(object sender, EventArgs e)
  {
  Rptstrconn = "select * from REWARD_PUNUSHMENT where STUDENT = " + "'" + txtrpt.Text.ToString().Trim() + "'";
  sqlrptconn = new SqlConnection(this.Rptconnstr);
  sqlrptda = new SqlDataAdapter(this.Rptstrconn, this.sqlrptconn);
  Rptset.Clear();

  sqlrptda.Fill(Rptset, "REWARD_PUNUSHMENT");
  datrpt.DataSource = Rptset.Tables[0];
  }

  private void button5_Click(object sender, EventArgs e)
  {
  int row = this.datrpt.VisibleRowCount;
  this.datrpt.CurrentCell = new DataGridCell(row + 1, 0);
  }

  private void RPT_Load(object sender, EventArgs e)
  {
  Rptstrconn = "select ID as 记录号,STUDENT as 学号,LEVEL as 奖惩代号,TIME as 奖惩时间,DESCRIPTION as 描述 from REWARD_PUNUSHMENT";
  sqlrptconn = new SqlConnection(this.Rptconnstr);
  sqlrptda = new SqlDataAdapter(this.Rptstrconn, this.sqlrptconn);
  Rptset.Clear();

  sqlrptda.Fill(Rptset, "REWARD_PUNUSHMENT");
  datrpt.DataSource = Rptset.Tables[0];
  }

  private void button4_Click(object sender, EventArgs e)
  {
  if (MessageBox.Show("您确定要退出系统吗？", "确认", MessageBoxButtons.OKCancel) == DialogResult.OK)
  this.Close();
  }

  private void button2_Click(object sender, EventArgs e)
  {
  int row = this.datrpt.VisibleRowCount;
  this.datrpt.CurrentCell = new DataGridCell(row + 1, 0);
  if (Rptset.HasChanges())
  {
  sqlrptconn = new SqlConnection(this.Rptconnstr);
  sqlrptda = new SqlDataAdapter(this.Rptstrconn, this.sqlrptconn);
  sqlrptcomm = new SqlCommandBuilder(sqlrptda);
  sqlrptda.Update(Rptset.GetChanges(), "REWARD_PUNUSHMENT");
  Rptset.AcceptChanges();
  MessageBox.Show("信息修改成功！");
  }
  }

  private void button3_Click(object sender, EventArgs e)
  {
  int rowNumber = this.datrpt.CurrentCell.RowNumber;
  //try
  //{
  this.Rptset.Tables[0].Rows[rowNumber].Delete();
  // DataSet Rptset = new DataSet();
  this.sqlrptconn = new SqlConnection(this.Rptconnstr);
  sqlrpt