Question

做C#.net 项目，如何使用app.config 文件来连接数据库，而不是反复的使用数据库连接代码（数据库为Access)

我用的可见化模式配置添加的数据源，因为产生了app.config 配置文件
app.config 中如下：<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
</configSections>
<connectionStrings>
<add name="ButterflyFinance.Properties.Settings.ButterflyConnectionString"
connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Butterfly.mdb"
providerName="System.Data.OleDb" />
</connectionStrings>
</configuration>

我想问下，具体如何使用来替代连接数据库语句，比如如何替代以下语句：
String ConStr ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Butterfly.mdb";
OleDbConnection oc = new OleDbConnection(ConStr);
oc.Open();
OleDbCommand dataCommand = new OleDbCommand();
dataCommand.Connection = oc;
dataCommand.CommandText = "select TOP 1 * from [User] where UserName = '" + UserName1 + "' and Password ='" + Password1 + "' ";
OleDbDataReader dr = dataCommand.ExecuteReader();
现经过试验把各位答案修正总结如下：
1。首先项目必须添加引用 System.Configuration
2。在本窗体 最前面 添加 using System.Configuration;
3。在代码这样替代String ConStr=ConfigurationManager.ConnectionStrings["ButterflyFinance.Properties.Settings.ButterflyConnectionString"].ConnectionString
或者String ConStr=System.Configuration.ConfigurationManager.ConnectionStrings["ButterflyFinance.Properties.Settings.ButterflyConnectionString"].ConnectionString

4。"ButterflyFinance.Properties.Settings.ButterflyConnectionString"可以在app.config中修改名称为ButterflyConnectionString 因此3。中代码可以简略为
String ConStr=ConfigurationManager.ConnectionStrings["ButterflyConnectionString"].ConnectionString

Answer 1

在web.config文件中写入以下语句：
<connectionStrings>
<add name="ButterflyFinance.Properties.Settings.ButterflyConnectionString"
connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Butterfly.mdb"
providerName="System.Data.OleDb" />
</connectionStrings>
在程序中用：
OleDbConnection con = new OleDbConnection(ConfigurationManager.ConnectionStrings["ButterflyFinance.Properties.Settings.ButterflyConnectionString"].ConnectionString);
代替：
String ConStr ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Butterfly.mdb";
OleDbConnection oc = new OleDbConnection(ConStr);
其他不变

Answer 2

你可以写一个方法或者类专门用来访问数据库，
public static OleDbConnection Con;
private static void open()
{
// open connection
if (Con == null)
{
try
{
string connectString = " Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Butterfly.mdb";
Con = new OleDbConnection(connectString);
Con.Open();
}
catch (Exception ex)
{
//输出错误
}
}
}
调用时只要一次调用open方法，就可以使用Con。。

Answer 3

包含命名空间System.Configuration
ConfigurationManager.ConnectionStrings("ButterflyFinance.Properties.Settings.ButterflyConnectionString").ConnectionString可取到

Answer 4

String ConStr=System.Configuration.ConfigurationManager.ConnectionStrings["ButterflyFinance.Properties.Settings.ButterflyConnectionString"].ConnectionString
使用前请确保项目已经引用 :System.Configuration这个程序集
------------------
问题解决.
你总结的也很正确.恭喜!

Answer 5

OleDbConnection oc = new OleDbConnection(ConfigurationManager.ConnectionStrings["ButterflyFinance.Properties.Settings.ButterflyConnectionString"].ConnectionString);