ASP.NET对SQLServer的通用数据库访问类

本文模仿实现数据库访问的通用类，代码清晰，而且很实用，包括了对数据库的所有的常用的操作。

  /// <summary>  /// 数据库访问通用类  /// </summary>  public class SqlHelper  {  private string connectionString;  /// <summary>  /// 设定数据库访问字符串  /// </summary>  public string ConnectionString  {  set { connectionString = value; }  }  /// <summary>  /// 构造函数  /// </summary>  /// <param name="connectionString">数据库访问字符串</param>  public SqlHelper(string connectionString)  {  this.connectionString = connectionString;  }  /// <summary>  /// 执行一个查询，并返回查询结果  /// </summary>  /// <param name="sql">要执行的sql语句</param>  /// <param name="commandType">要执行的查询语句的类型，如存储过程或者sql文本命令</param>  /// <returns>返回查询结果集</returns>  public DataTable ExecuteDataTable(string sql,CommandType commandType)  {  return ExecuteDataTable(sql, commandType, null);  }  /// <summary>  /// 执行一个查询，并返回结果集  /// </summary>  /// <param name="sql">要执行的sql文本命令</param>  /// <returns>返回查询的结果集</returns>  public DataTable ExecuteDataTable(string sql)  {  return ExecuteDataTable(sql, CommandType.Text, null);  }  /// <summary>  /// 执行一个查询，并返回查询结果  /// </summary>  /// <param name="sql">要执行的sql语句</param>  /// <param name="commandtype">要执行查询语句的类型，如存储过程或者sql文本命令</param>  /// <param name="parameters">Transact-SQL语句或者存储过程参数数组</param>  /// <returns></returns>  public DataTable ExecuteDataTable(string sql, CommandType commandtype, SqlParameter[] parameters)  {  DataTable data = new DataTable(); //实例化datatable，用于装载查询结果集  using (SqlConnection con = new SqlConnection(connectionString))  {  using (SqlCommand cmd = new SqlCommand(sql, con))  {  cmd.CommandType = commandtype;//设置command的commandType为指定的Commandtype  //如果同时传入了参数，则添加这些参数  if (parameters != null)  {  foreach (SqlParameter parameter in parameters)  {  cmd.Parameters.Add(parameter);  }  }  //通过包含查询sql的sqlcommand实例来实例化sqldataadapter  SqlDataAdapter adapter = new SqlDataAdapter(cmd);  adapter.Fill(data);//填充datatable  }  }  return data;  }  /// <summary>  /// 返回一个SqlDataReader对象的实例  /// </summary>  /// <param name="sql">要执行的SQl查询命令</param>  /// <returns></returns>  public SqlDataReader ExecuteReader(string sql)  {  return ExecuteReader(sql, CommandType.Text, null);  }  /// <summary>  ///  /// </summary>  /// <param name="sql">要执行的sql语句</param>  /// <param name="commandType">要执行查询语句的类型，如存储过程或者SQl文本命令</param>  /// <returns></returns>  public SqlDataReader ExecuteReader(string sql,CommandType commandType)  {  return ExecuteReader(sql, commandType, null);  }  /// <summary>  /// 返回一个sqldatareader对象的实例  /// </summary>  /// <param name="sql"></param>  /// <param name="commandType"></param>  /// <param name="parameters"></param>  /// <returns></returns>  public SqlDataReader ExecuteReader(string sql, CommandType commandType, SqlParameter[] parameters)  {  SqlConnection con = new SqlConnection(connectionString);  SqlCommand cmd = new SqlCommand(sql, con);  if (parameters != null)  {  foreach (SqlParameter parameter in parameters)  {  cmd.Parameters.Add(parameters);  }  }  con.Open();  //CommandBehavior.CloseConnection参数指示关闭reader对象时关闭与其关联的Connection对象  return cmd.ExecuteReader(CommandBehavior.CloseConnection);  }  /// <summary>  /// 执行一个查询，返回结果集的首行首列。忽略其他行，其他列  /// </summary>  /// <param name="sql">要执行的SQl命令</param>  /// <returns></returns>  public Object ExecuteScalar(string sql)  {  return ExecuteScalar(sql, CommandType.Text, null);  }  /// <summary>  ///  /// </summary>  /// <param name="sql"></param>  /// <param name="commandType"></param>  /// <returns></returns>  public Object ExecuteScalar(string sql, CommandType commandType)  {  return ExecuteScalar(sql, commandType, null);  }  /// <summary>  ///  /// </summary>  /// <param name="sql"></param>  /// <param name="commandType">参数类型</param>  /// <param name="parameters"></param>  /// <returns></returns>  public Object ExecuteScalar(string sql,CommandType commandType, SqlParameter[] parameters)  {  Object result=null;  SqlConnection con=new SqlConnection(connectionString);  SqlCommand cmd=new SqlCommand(sql,con);  cmd.CommandType= commandType;  if(parameters!=null)  {  foreach (SqlParameter parapmeter in parameters)  {  cmd.Parameters.Add(parapmeter);  }  }  con.Open();  result=cmd.ExecuteScalar();  con.Close();  return result;  }  /// <summary>  /// 对数据库进行增删改的操作  /// </summary>  /// <param name="sql">要执行的sql命令</param>  /// <returns></returns>  public int ExecuteNonQuery(string sql)  {  return ExecuteNonQuery(sql, CommandType.Text, null);  }  /// <summary>  /// 数据库进行增删改的操作  /// </summary>  /// <param name="sql">对数据库进行操作的sql命令</param>  /// <param name="commandType">要执行查询语句的类型，如存储过程或者sql文本命令</param>  /// <returns></returns>  public int ExecuteNonQuery(string sql, CommandType commandType)  {  return ExecuteNonQuery(sql, commandType, null);  }  /// <summary>  /// 对数据库进行增删改的操作  /// </summary>  /// <param name="sql">要执行的sql语句</param>  /// <param name="commandType">要执行的查询语句类型，如存储过程或者sql文本命令</param>  /// <param name="parameters">Transact-SQL语句或者存储过程的参数数组</param>  /// <returns></returns>  public int ExecuteNonQuery(string sql, CommandType commandType, SqlParameter[] parameters)  {  int count = 0;  SqlConnection con = new SqlConnection(connectionString);  SqlCommand cmd = new SqlCommand(sql, con);  cmd.CommandType = commandType;  if (parameters != null)  {  foreach(SqlParameter parameter in parameters)  {  cmd.Parameters.Add(parameter);  }  }  con.Open();  count = cmd.ExecuteNonQuery();  con.Close();  return count;  }  /// <summary>  /// 返回当前连接的数据库中所有用户创建的数据库  /// </summary>  /// <returns></returns>  public DataTable GetTables()  {  DataTable table = null;  using (SqlConnection con = new SqlConnection(connectionString))  {  con.Open();  table = con.GetSchema("Tables");  }  return table;  }  }