public async Task Exists() { // Check if a package exists. NuGetClient client = new NuGetClient("https://api.nuget.org/v3/index.json"); if (!await client.ExistsAsync("newtonsoft.json")) { Console.WriteLine("Package 'newtonsoft.json' does not exist!"); } var packageVersion = NuGetVersion.Parse("12.0.1"); if (!await client.ExistsAsync("newtonsoft.json", packageVersion)) { Console.WriteLine("Package 'newtonsoft.json' version '12.0.1' does not exist!"); } }