public async Task QueryTwinsAsync()
{
PrintHeader("QUERY DIGITAL TWINS");
try
{
Console.WriteLine("Making a twin query and iterating over the results.");
#region Snippet:DigitalTwinsSampleQueryTwins
// This code snippet demonstrates the simplest way to iterate over the digital twin results, where paging
// happens under the covers.
AsyncPageable <string> asyncPageableResponse = client.QueryAsync("SELECT * FROM digitaltwins");
// Iterate over the twin instances in the pageable response.
// The "await" keyword here is required because new pages will be fetched when necessary,
// which involves a request to the service.
await foreach (string response in asyncPageableResponse)
{
BasicDigitalTwin twin = JsonSerializer.Deserialize <BasicDigitalTwin>(response);
Console.WriteLine($"Found digital twin '{twin.Id}'");
}
#endregion Snippet:DigitalTwinsSampleQueryTwins
Console.WriteLine("Making a twin query, with query-charge header extraction.");
#region Snippet:DigitalTwinsSampleQueryTwinsWithQueryCharge
// This code snippet demonstrates how you could extract the query charges incurred when calling
// the query API. It iterates over the response pages first to access to the query-charge header,
// and then the digital twin results within each page.
AsyncPageable <string> asyncPageableResponseWithCharge = client.QueryAsync("SELECT * FROM digitaltwins");
int pageNum = 0;
// The "await" keyword here is required as a call is made when fetching a new page.
await foreach (Page <string> page in asyncPageableResponseWithCharge.AsPages())
{
Console.WriteLine($"Page {++pageNum} results:");
// Extract the query-charge header from the page
if (QueryChargeHelper.TryGetQueryCharge(page, out float queryCharge))
{
Console.WriteLine($"Query charge was: {queryCharge}");
}
// Iterate over the twin instances.
// The "await" keyword is not required here as the paged response is local.
foreach (string response in page.Values)
{
BasicDigitalTwin twin = JsonSerializer.Deserialize <BasicDigitalTwin>(response);
Console.WriteLine($"Found digital twin '{twin.Id}'");
}
}
#endregion Snippet:DigitalTwinsSampleQueryTwinsWithQueryCharge
}
catch (Exception ex)
{
FatalError($"Could not query digital twins due to {ex}");
}
}
