ADO.NET 连接数据库的另一种方法（通过配置文件和基类转化，适用于后期维护）

本文参考C#高级编程（第七版）30.2

首先是书上一个简单的数据库连接的demo

using System;
using System.Data.SqlClient;

public class ExecuteNonQueryExample
{
public static void Main(string[] args)
{
string source = "server=(local);" +
"integrated security=SSPI;" +
"database=Northwind";
string select = "UPDATE Customers " +
"SET ContactName = 'Bob' " +
"WHERE ContactName = 'Bill'";
SqlConnection  conn = new SqlConnection(source);
conn.Open();
SqlCommand cmd = new SqlCommand(select, conn);
int rowsReturned = cmd.ExecuteNonQuery();
Console.WriteLine("{0} rows returned.", rowsReturned);
conn.Close();
}
}

为了方便管理连接数据库，更为了后期维护的方便。采用另外一种方式

将数据库的的配置信息放到配置文件（app.config）中，如下

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="db"
providerName="System.Data.SqlClient"
connectionString="server=(local)\SQLEXPRESS;integrated security=SSPI;database=test;" />
</connectionStrings>
</configuration>

 其次为了让适用于各种类型的数据库，将连接方式专门新建一个静态类，命名databases.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Common;
using System.Configuration;

namespace ConsoleApplication1
{
static class databases
{
static public DbConnection GetDatabaseConnection(string name)
{
ConnectionStringSettings settings =
ConfigurationManager.ConnectionStrings[name];

DbProviderFactory factory = DbProviderFactories.GetFactory(settings.ProviderName);

DbConnection conn = factory.CreateConnection();
conn.ConnectionString = settings.ConnectionString;

return conn;
}
}
}

如果出现 ConnectionStringSettings 无法识别的情况，需要在解决方案的那里引用一个System.Configuration

那么新的数据库操作方式就是

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Data.Common;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
string select = "insert into person(name,sex) values('bb','sb')";
try
{
//返回DbConnection类型的连接，强制转换成SqlConnection类型，SqlConnection用以连接sql server数据库
using (SqlConnection conn = (SqlConnection)databases.GetDatabaseConnection("db"))
{

conn.Open();
SqlCommand cmd = new SqlCommand(select, conn);
int rowsReturned = cmd.ExecuteNonQuery();
Console.WriteLine("{0} rows returned.", rowsReturned);
conn.Close();
Console.ReadLine();
}
//useing的对象在结束后会自动销毁对象。
}
catch(SqlException e)
{
throw e;
}
}

}
}