初学ADO.NET时写的数据库访问类[5]

  /// <summary>
  /// //返回DataSet
  /// </summary>
  public DataSet ExeSqlDs(string strSql, int nStart, int nCount, string strTable)
  {
   m_strError = "";
   SqlDataAdapter sqlAdapter = new SqlDataAdapter(strSql,m_sqlCnn);
   DataSet dbSet = new DataSet();
   try
   {
    sqlAdapter.Fill(dbSet,nStart,nCount,strTable);
   }
   catch (SqlException ex)
   {
    dbSet = null;
    m_strError = ex.ToString();
   }
   return dbSet;
  }

  //返回DataReader
  public SqlDataReader ExeSqlDr(string strSql)
  {
   m_strError = "";
   SqlDataReader dr = null;
   SqlCommand sqlCmd = new SqlCommand(strSql,m_sqlCnn);
   try
   {
    OpenCnn();
    dr = sqlCmd.ExecuteReader();
   }
   catch (SqlException ex)
   {
    dr = null;
    m_strError = ex.ToString();
   }
   finally
   {
    if (m_sqlCnn.State==ConnectionState.Open)
    {
     sqlCmd.Dispose();
    }
   }
   return dr;
  }

  /// <summary>
  /// 执行ExecuteScalar
  /// </summary>
  public int ExeScalar(string strSql)
  {
   int nCount = -1;
   m_strError = "";
   SqlCommand sqlCmd = new SqlCommand(strSql,m_sqlCnn);
   try
   {
    OpenCnn();
    nCount = (int)sqlCmd.ExecuteScalar();
   }
   catch (SqlException ex)
   {
    nCount = -1;
    m_strError = ex.ToString();
   }
   finally
   {
    if (m_sqlCnn.State==ConnectionState.Open)
    {
     sqlCmd.Dispose();
     m_sqlCnn.Close();
    }
   }
   return nCount;
  }

  /// <summary>
  /// 打开Connection
  /// </summary>
  private void OpenCnn()
  {
   if (m_sqlCnn.State==ConnectionState.Open)
   {
    m_sqlCnn.Close();
   }
   m_sqlCnn.Open();
  }

  /// <summary>
  /// 返回DataSet
  /// </summary>
  public DataSet ExeSqlDs(SqlCommand sqlCmd, string strTable)
  {
   m_strError = "";
   DataSet ds = new DataSet();
   sqlCmd.Connection = m_sqlCnn;
   SqlDataAdapter sqlAdapter = new SqlDataAdapter();
   sqlAdapter.SelectCommand = sqlCmd;
   try
   {
    sqlAdapter.Fill(ds,strTable);
   }
   catch (SqlException ex)
   {
    ds = null;
    m_strError = ex.ToString();
   }
   return ds;
  }

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

  /// <summary>
  /// 错误信息
  /// </summary>

  private string m_strError;

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