在winform下取app.config文件中的值
app.config文件的内容如下：
<?xml   version= "1.0 "   encoding= "utf-8 "   ?>
<configuration>
    <ConnectionStrings>
                <add   name= "OracleConnectionString "
                        connectionString= "Data   Source=db;User   ID=system;Unicode=True "
                        providerName= "System.Data.OracleClient "   />
        </ConnectionStrings>
    </configuration>

form.cs代码如下：
richTextBox1.Text   =   System.Configuration.ConfigurationManager.ConnectionStrings[ "OracleConnectionString "].ToString();

结果提示为,未将对象引用设置到对象的实例
我原来只用过web   中的web.config,是可以的，请问为什么取不到值？

------解决方案--------------------
<?xml version= "1.0 " encoding= "utf-8 " ?>
<configuration>
<connectionStrings>
<add name= "test " connectionString= "Data Source=test;Initial Catalog=SIS;Persist Security Info=True;User ID=admin;Password=admin "
providerName= "System.Data.SqlClient " />
</connectionStrings>
</configuration>

private void Form1_Load(object sender, EventArgs e)
{
textBox1.Text =
System.Configuration.ConfigurationManager.ConnectionStrings[ "test "].ToString();
}