c#程序获取winfrom项目app.config对的配置文件及修改
<?xml version="1.0"?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
  </startup>
<appSettings>
  <add key="ConnectionString" value="server=.;user id=sa;password=sa;database=base;" />
  </appSettings>
</configuration>

怎么知道是连接失败了呢？小弟不才 刚接触数据库  求各位大神指点   
------解决方案--------------------
string s = ConfigurationManager.AppSettings["ConnectionString"].ToString();