PM> Install-Package Harvest.Api

var client = HarvestClient.FromAccessToken("user_agent", "access_token");

var projects = await client.GetProjectAssignmentsAsync();

var client = new HarvestClient("HavestApiClient")
{
    ClientId = "<ClientId>",
    ClientSecret = "<ClientSecret>",
    RedirectUri = new Uri("http://redirect/url"),
};

var authUrl = auth.BuildAuthorizationUrl();

// open url via web browser component for WPF, Windows Forms application or redirect to this url for asp.net application

// you can use helper to parse redirect url 
var client = await client.AuthorizeAsync(callbackUri);

// OR for existing accessToken/personal access token

client.Authorize(accessToken);

// OR

var client = HarvestClient.FromAccessToken("HavestApiClient", accessToken);