// Either use from config
const GmailScopes scopes = GmailScopes.Readonly | GmailScopes.Compose;
string privateKey = SettingsManager.GetPrivateKey();
string tokenUri = SettingsManager.GetTokenUri();
string clientEmail = SettingsManager.GetClientEmail();
string emailAddress = SettingsManager.GetEmailAddress();
ServiceAccountCredential accountCredential = new ServiceAccountCredential
{
    PrivateKey = privateKey,
    TokenUri = tokenUri,
    ClientEmail = clientEmail
};
var client = new GmailClient(accountCredential, emailAddress, scopes);

// Or use from downloaded JSON file directly
const string path = "C:\\Users\\Me\\Documents\\Gmail-Project.json";
var initializer = GmailClientInitializer.Initialize(path, scopes);
client = new GmailClient(initializer, emailAddress);

// Send a plain text email
Message sentMessage = await client.Messages.SendAsync(emailAddress, "The subject", "Plain text body");

// Send a HTML email
sentMessage = await client.Messages.SendAsync(emailAddress, "The subject", "<h1>HTML body</h1>", isBodyHtml: true);

// Get the users profile
Profile profile = await client.GetProfileAsync();

// Get inbox messages
IList<Message> messages = await client.Messages.ListAsync();

// Get starred messages
IList<Message> starredMessages = await client.Messages.ListByLabelAsync(Label.Starred);

// List all labels
IList<Label> labels = await client.Labels.ListAsync();

// List all drafts
IList<Draft> drafts = await client.Drafts.ListAsync();