Yes the User can able to see the value. It will be saved in a XML file. This file will be located in your application Folder
This will be stored in the
Code:
<c:\Documents and Settings>\<username>\[Local Settings\]Application Data\<companyname>\<appdomainname>_<eid>_<hash>\<verison>.
Code:
<applicationSettings>
<MySettingsDemo.MySettings>
<setting name="SMTPServerIP" serializeAs="String">
<value>127.0.0.1</value>
</setting>
<setting name="MyServicesURL" serializeAs="String">
<value>http://localhost/myservices.asmx</value>
</setting>
</MySettingsDemo.MySettings>
</applicationSettings>
MSDN