C#学习教程：在3层架构中使用BAL？如何从DAL调用方法到BAL分享

通常我会做以下事情：

1. 定义业务层（BL，您将其称为BAL）。 这包含您的业务实体的定义。 它还定义了用于检索/保存/删除您使用的任何模式（存储库，上下文等）的数据的接口。
2. 定义数据访问层（DAL）。 这包含检索/保存/删除接口的实际实现。
3. 定义UI图层。 这包含UI元素（表单，控件，模型，控制器等），它们可以使用BL来加载数据。

参考文献如下：

1. BL不知道DAL或UI。
2. DAL知道BL。 DAL不知道UI。
3. UI知道BL。 用户界面不知道DAL。

对你来说最大的问题是，当BL不知道DAL时，BL如何检索/保存/删除数据，因此无法在DAL中创建类的实例。 好吧，这是一个小dependency injection派上用场的地方。 你需要接线的就是将DAL类注入BL接口。

希望这是有道理的。 我将它用作我的标准3层实现，它绝对没有问题。 具体来说，我使用entity framework和POCO实体，我使用的DI是自定义的，但任何一个都可以。

UPDATE

BL不知道DAL。

我希望这更有意义。

您可以使用以下3层架构的示例代码： &＃8211;

CLASS &＃8211; BAL.cs

 using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Collections; public class BAL { DAL objDAL; public BAL() { } public string _Name; public string Name { get { return _Name; } set { _Name = value; } } public int insert() { objDAL = new DAL(); int val = 0; try { Hashtable objHash = new Hashtable(); objHash.Add("@Name", Convert.ToString(_Name)); val = objDAL.Insert("Your SP Name", objHash); } catch (Exception ex) { throw ex; } finally { objDAL = null; } return val; } } 

CLASS &＃8211; DAL.cs

 using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Data; using System.Data.SqlClient; using System.Collections; public class DAL : IDisposable { SqlConnection con; public DAL() { con = new SqlConnection("Connection String"); } public int Insert(string CMD, Hashtable objHash) { int val = 0; try { SqlCommand cmd1 = new SqlCommand(CMD, con); cmd1.CommandType = CommandType.StoredProcedure; foreach (DictionaryEntry de in objHash) { cmd1.Parameters.AddWithValue(Convert.ToString(de.Key), Convert.ToString(de.Value)); } con.Open(); val = cmd1.ExecuteNonQuery(); } catch (Exception ex) { throw ex; } finally { con.Close(); } return val; } #region IDisposable Members public void Dispose() { throw new NotImplementedException(); } #endregion } 

用户界面： &＃8211;

 using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; public partial class _Default : System.Web.UI.Page { BAL objBAL; protected void Page_Load(object sender, EventArgs e) { Insert(); } public void Insert() { int val = 0; objBAL = new BAL(); objBAL.Name = "stackoverflow"; try { val = objBAL.insert(); } catch { } finally { objBAL = null; } if (val != 0) { //Insert sucessful } else { //Error in Insert. } } } 

希望这会有所帮助。

它可能会帮助您查看一些实际代码。 我建议您下载NetTiers ，针对您的数据库模式运行它，并查看输出的代码以获取实现细节。

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 using System; using System.Data; using System.Configuration; using System.Collections.Generic; using System.Text; using System.Data.Common; using System.Data.SqlClient; using System.Data.OleDb; using System.Data.Odbc; using System.IO; using System.ComponentModel; namespace dal { /// 
 /// Summary description for Data Access Layer /// 
 public class DataAccess { public string strConnectionString; private DbConnection objConnection; private DbCommand objCommand; private DbProviderFactory objFactory = null; private bool boolHandleErrors=false; private string strLastError; private bool boolLogError=false; private string strLogFile; public DataAccess() { //strCOnnectionString= ; strCOnnectionString= objCommon.GetConnectionString; objFactory = OleDbFactory.Instance; objCOnnection= objFactory.CreateConnection(); objCommand = objFactory.CreateCommand(); objConnection.COnnectionString= strConnectionString; objCommand.COnnection= objConnection; } public bool HandleErrors { get { return boolHandleErrors; } set { boolHandleErrors = value; } } public string LastError { get { return strLastError; } } public bool LogErrors { get - { return boolLogError; } set { boolLogError = value; } } public string LogFile { get { return strLogFile; } set { strLogFile = value; } } public int AddParameter(string name, object value) { DbParameter p = objFactory.CreateParameter(); p.ParameterName = name; p.Value = value; return objCommand.Parameters.Add(p); } public int AddParameter(string name, object value, ParameterDirection direction) { DbParameter p = objFactory.CreateParameter(); p.ParameterName = name; p.Value = value; p.Direction = direction; return objCommand.Parameters.Add(p); } public int AddParameter(string name, object value, DbType type) { DbParameter p = objFactory.CreateParameter(); p.ParameterName = name; p.Value = value; p.DbType = type; return objCommand.Parameters.Add(p); } public int AddParameter(DbParameter parameter) { return objCommand.Parameters.Add(parameter); } public DbCommand Command { get { return objCommand; } } public void BeginTransaction() { try { if (objConnection.State == System.Data.ConnectionState.Closed) { objConnection.Open(); } objCommand.Transaction = objConnection.BeginTransaction(); } catch (Exception Ex) { HandleExceptions(Ex); } } public void CommitTransaction() { objCommand.Transaction.Commit(); objConnection.Close(); } public void RollbackTransaction() { objCommand.Transaction.Rollback(); objConnection.Close(); } public int ExecuteNonQuery(string query) { return ExecuteNonQuery(query, CommandType.Text, ConnectionState.CloseOnExit); } public int ExecuteNonQuery(string query, CommandType commandtype) { return ExecuteNonQuery(query, commandtype, ConnectionState.CloseOnExit); } public int ExecuteNonQuery(string query, ConnectionState connectionstate) { return ExecuteNonQuery(query, CommandType.Text, connectionstate); } public int ExecuteNonQuery(string query, CommandType commandtype, ConnectionState connectionstate) { objCommand.CommandText = query; objCommand.CommandType = commandtype; int i = -1; try { if (objConnection.State == System.Data.ConnectionState.Closed) { objConnection.Open(); } i = objCommand.ExecuteNonQuery(); } catch (Exception ex) { HandleExceptions(ex); } finally { objCommand.Parameters.Clear(); if (cOnnectionstate== ConnectionState.CloseOnExit) { objConnection.Close(); } } return i; } public object ExecuteScalar(string query) { return ExecuteScalar(query, CommandType.Text, ConnectionState.CloseOnExit); } public object ExecuteScalar(string query, CommandType commandtype) { return ExecuteScalar(query, commandtype, ConnectionState.CloseOnExit); } public object ExecuteScalar(string query, ConnectionState connectionstate) { return ExecuteScalar(query, CommandType.Text, connectionstate); } public object ExecuteScalar(string query, CommandType commandtype, ConnectionState connectionstate) { objCommand.CommandText = query; objCommand.CommandType = commandtype; object o = null; try { if (objConnection.State == System.Data.ConnectionState.Closed) { objConnection.Open(); } o = objCommand.ExecuteScalar(); } catch (Exception ex) { HandleExceptions(ex); } finally { objCommand.Parameters.Clear(); if (cOnnectionstate== ConnectionState.CloseOnExit) { objConnection.Close(); } } return o; } public DbDataReader ExecuteReader(string query) { return ExecuteReader(query, CommandType.Text, ConnectionState.CloseOnExit); } public DbDataReader ExecuteReader(string query, CommandType commandtype) { return ExecuteReader(query, commandtype, ConnectionState.CloseOnExit); } public DbDataReader ExecuteReader(string query, ConnectionState connectionstate) { return ExecuteReader(query, CommandType.Text, connectionstate); } public DbDataReader ExecuteReader(string query, CommandType commandtype, ConnectionState connectionstate) { objCommand.CommandText = query; objCommand.CommandType = commandtype; DbDataReader reader = null; try { if (objConnection.State == System.Data.ConnectionState.Closed) { objConnection.Open(); } if (cOnnectionstate== ConnectionState.CloseOnExit) { reader = objCommand.ExecuteReader(CommandBehavior.CloseConnection); } else { reader = objCommand.ExecuteReader(); } } catch (Exception ex) { HandleExceptions(ex); } finally { objCommand.Parameters.Clear(); } return reader; } public DataSet ExecuteDataSet(string query) { return ExecuteDataSet(query, CommandType.Text, ConnectionState.CloseOnExit); } public DataSet ExecuteDataSet(string query, CommandType commandtype) { return ExecuteDataSet(query, commandtype, ConnectionState.CloseOnExit); } public DataSet ExecuteDataSet(string query, ConnectionState connectionstate) { return ExecuteDataSet(query, CommandType.Text, connectionstate); } public DataSet ExecuteDataSet(string query, CommandType commandtype, ConnectionState connectionstate) { DbDataAdapter adapter = objFactory.CreateDataAdapter(); objCommand.CommandText = query; objCommand.CommandType = commandtype; adapter.SelectCommand = objCommand; DataSet ds = new DataSet(); try { adapter.Fill(ds); } catch (Exception ex) { HandleExceptions(ex); } finally { objCommand.Parameters.Clear(); if (cOnnectionstate== ConnectionState.CloseOnExit) { if (objConnection.State == System.Data.ConnectionState.Open) { objConnection.Close(); } } } return ds; } private void HandleExceptions(Exception ex) { throw ex; } private void WriteToLog(string msg) { StreamWriter writer = File.AppendText(LogFile); writer.WriteLine(DateTime.Now.ToString() + " - " + msg); writer.Close(); } public void Dispose() { objConnection.Close(); objConnection.Dispose(); objCommand.Dispose(); } public enum Providers { SqlServer, OleDb, Oracle, ODBC, ConfigDefined } public enum ConnectionState { KeepOpen, CloseOnExit } public interface ILoadFromDataRow { bool LoadFromDataRow(DataRow row); } } }