public async Task TestStream()
{
var tenCodes = await GetTenRandomIso2Codes();
var countries = IoTDataSource.DownloadCountriesStream(tenCodes);
// "await foreach" is a new keyword thatcan be applied to a variable that implements IAsyncEnumerable<T>.
await foreach (var country in countries)
{
output.WriteLine(country.GetProperty("name").GetString());
}
}
private async Task <string[]> GetTenRandomIso2Codes()
{
// Download a hundred Iso2Codes from worldbank.org.
JsonElement.ArrayEnumerator array = await IoTDataSource.FetchJsonFromUrl("http://api.worldbank.org/v2/country?format=json&per_page=100");
// Remove array wrapper from the Json.
JsonElement.ArrayEnumerator countries = array.Current.EnumerateArray();
// Select iso2Codes from array of countries.
string[] iso2Codes = countries.Select(c => c.GetProperty("iso2Code").GetString()).ToArray();
// Take 10 sequential codes from the hundred of country data.
var random = new System.Random();
return(Enumerable.Range(0, 10).Select(i => random.Next(i * 10, i * 10 + 10)).Select(i => iso2Codes[i]).ToArray());
}
