ConfigurationSettings.AppSettings is obsolete, warning

var values = new NameValueCollection
{
    { "key", ConfigurationSettings.AppSettings["API-Key"].ToString() },
    { "image", Convert.ToBase64String(File.ReadAl开发者_如何学运维lBytes(photo.ToString())) }
};

What's the new way to use the app.config file?

The ConfigurationManager class in System.Configuration:

ConfigurationManager.AppSettings

ConfigurationManager.ConnectionStrings

So your code would change to:

var values = new NameValueCollection 
{ 
    { "key", ConfigurationManager.AppSettings["API-Key"] }, 
    { "image", Convert.ToBase64String(File.ReadAllBytes(photo.ToString())) } 
}; 

Make sure you add a reference to System.Configuration along with the using statement for System.Configuration.

Use the System.Configuration.ConfigurationManager class

string ServerName = System.Configuration.ConfigurationManager.AppSettings["Servername"];

Edit - added

Note, you may have to add a reference to System.Configuration.dll. Even if you can import the namespace without the reference, you will not be able to access this class unless you have the reference.

With the ConfigurationManager class

http://msdn.microsoft.com/en-us/library/system.configuration.configurationmanager.aspx

The new class to use is the ConfigurationManager class.