/// <summary>
/// Initializes a new instance based on the specified refresh token.
/// </summary>
/// <param name="clientId">The client ID.</param>
/// <param name="clientSecret">The client secret.</param>
/// <param name="refreshToken">The refresh token of the user.</param>
public static BoxService CreateFromRefreshToken(string clientId, string clientSecret, string refreshToken) {
// Initialize a new OAuth client
BoxOAuthClient client = new BoxOAuthClient(clientId, clientSecret);
// Get an access token from the refresh token.
BoxTokenResponse response = client.GetAccessTokenFromRefreshToken(refreshToken);
// Update the OAuth client with the access token
client.AccessToken = response.Body.AccessToken;
// Initialize a new service instance
return new BoxService(client);
}