初学ADO.NET时写的数据库访问类[3]

  /// <summary>
  /// 返回DataSet
  /// </summary>
  public DataSet ExeSqlDs(string strSql, int nStart, int nCount, string strTable)
  {
   m_strError = "";
   DataSet ds = new DataSet();
   OleDbDataAdapter oleDbAdapter = new OleDbDataAdapter(strSql,m_oleDbCnn);
   try
   {
    oleDbAdapter.Fill(ds,nStart,nCount,strTable);
   }
   catch (OleDbException ex)
   {
    ds = null;
    m_strError = ex.ToString();
   }
   return ds;
  }

  /// <summary>
  /// 返回DataSet
  /// </summary>
  public DataSet ExeSqlDs(OleDbCommand oleDbCmd, string strTable)
  {
   m_strError = "";
   DataSet ds = new DataSet();
   oleDbCmd.Connection = m_oleDbCnn;
   OleDbDataAdapter oleDbAdapter = new OleDbDataAdapter();
   oleDbAdapter.SelectCommand = oleDbCmd;
   try
   {
    oleDbAdapter.Fill(ds,strTable);
   }
   catch (OleDbException ex)
   {
    ds = null;
    m_strError = ex.ToString();
   }
   return ds;
  }

  /// <summary>
  /// //设定Connection 字符串，new cnn
  /// </summary>
  public void SetConnectionString(string strSource)
  {
   m_strCnn = strSource;
   m_oleDbCnn = null;
   m_oleDbCnn = new OleDbConnection(m_strCnn);
  }

  /// <summary>
  /// 错误信息
  /// </summary>
  private string m_strError;

  /// <summary>
  /// 错误
  /// </summary>
  public string StrErrorInfo
  {
   get
   {
    return m_strError;
   }
  }
 }
}

/*************************************************

SqlDb

**************************************************/

using System;
using System.IO;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace Db
{
 /// <summary>
 ///
 /// </summary>
 public class SqlDb
 {
  
  public SqlDb()
  {
   //
   // TODO: 在此处添加构造函数逻辑
   m_sqlCnn = null;
   //
  }

  /// <summary>
  /// Connection参数
  /// </summary>
  private string m_strCnn;   // = System.Configuration.ConfigurationSettings.AppSettings["ConnectionString"];
  private SqlConnection m_sqlCnn = null;    //new SqlConnection(m_strCnn);

  /// <summary>
  /// 执行delete，insert，update等操作，返回值为影响的行数
  /// </summary>
  public int ExeNoQuery(string strSql)
  {
   int nRet = -1;
   m_strError = "";
   SqlCommand sqlCmd = new SqlCommand(strSql,m_sqlCnn);
   try
   {
    OpenCnn();
    nRet = sqlCmd.ExecuteNonQuery();
   }
   catch (SqlException ex)
   {
    nRet = -1;
    m_strError = ex.ToString();
   }
   finally
   {
    if (m_sqlCnn.State==ConnectionState.Open)
    {
     sqlCmd.Dispose();
     m_sqlCnn.Close();
    }
   }
   return nRet;
  }