Retrieving resource history

There are several ways to retrieve version history for resources using the FhirClient.

Note

Servers are not required to support version retrieval. If the history interaction is supported, the server may choose which levels it supports. You can check the server’s CapabilityStatement to see what is available.

History of a specific resource

You can retrieve the version history of a specific resource using the HistoryAsync method of the FhirClient. You may specify a date to include only changes made after that date, and a count to limit the number of results returned.

The method returns a Bundle resource containing the history for the resource instance. For example:

var pat_31_hist = await client.HistoryAsync("Patient/31");
// or
var pat_31_hist = await client.HistoryAsync("Patient/31", new FhirDateTime("2016-11-29").ToDateTimeOffset());
// or
var pat_31_hist = await client.HistoryAsync("Patient/31", new FhirDateTime("2016-11-29").ToDateTimeOffset(), 5);

Note

The Bundle may contain entries without a resource if a version was created by a delete interaction.

History for a resource type

Sometimes you may want to retrieve the history for a type of resource rather than a single instance (for example, all versions of Patient resources). In this case, use the TypeHistoryAsync method:

var pat_hist = await client.TypeHistoryAsync<Patient>();

As with the instance-level method, you can optionally specify a date and page size.

System-wide history

To retrieve the history for all resources in the system, use the WholeSystemHistoryAsync method of the FhirClient. You can specify a date and a page size:

var lastMonth = DateTime.Today.AddMonths(-1);
var last_month_hist = await client.WholeSystemHistoryAsync(since: lastMonth, pageSize: 10);

This function retrieves all changes to all resources made since the specified date and limits the results to the given maximum. See Paged results for an example of how to page through the resulting Bundle.