Question

C#三层架构中如何公用连接数据库和增删改查等功能

把连接数据库字符串和增删改查等SQL语名写在一个类里面，调用。那么这个类是属于哪个层的，如何去写啊？？？

Answer 1

既然是3层架构了
那么数据访问就一定要交给数据层了
也就是说所有与数据库打交道的方法都写在数据层，表现层和业务层都不会使用到数据库连接字符串。而且我一般把链接字符串写在配置文件里（web.config）
<connectionStrings>
<add name="YourString" connectionString="？？？？？"
providerName="System.Data.SqlClient" />
</connectionStrings>

该节点存在于<configuration>中 在访问的时候使用ConfigurationManager.ConnectionStrings["YourString"].ConnectionString 访问此链接字符串

Answer 2

namespace DBUtility
{
public abstract class DbHelperSQL
{
private static DbConnection objConnection;
private static DbCommand objCommand;
private static DbProviderFactory objFactory = null;
private static bool boolHandleErrors;
private static string strLastError;
private static bool boolLogError;
private static string strLogFile;

static DbHelperSQL()
{
string strConnectionString = ConfigurationManager.ConnectionStrings["conn_Config"].ConnectionString;
string providername = ConfigurationManager.ConnectionStrings["conn_Config"].ProviderName;
switch (providername)
{
case "System.Data.SqlClient":
objFactory = SqlClientFactory.Instance;
break;
case "System.Data.OleDb":
objFactory = OleDbFactory.Instance;
break;
case "System.Data.OracleClient":
objFactory = OracleClientFactory.Instance;
break;
case "System.Data.Odbc":
objFactory = OdbcFactory.Instance;
break;
}

objConnection = objFactory.CreateConnection();
objCommand = objFactory.CreateCommand();
objConnection.ConnectionString = strConnectionString;
objCommand.Connection = objConnection;
}

数据访问层

Answer 3

属于数据层，C#2008中你可以直接用数据实体功能，向导会根据你的数据库自动创建这个ORM

Answer 4

属于数据链路层

Answer 5

放到数据访问层，即DALC