PI WebAPI remove cache instance for a user fails.

Question

Hi,

I would like to remove a PI WebAPI cache instance for a user from C# code but it fails.

I know the implications, you should not do this on a regular basis, but I still want to be able to do it.

When I look at the available documentation here:

and here:

I should do a DELETE request to the PI WebAPI with the SID of the user.

So I suppose my C# code would look like this (simplified):

using var client = new HttpClient();

string url = "https://mypiweb/piwebapi/system/cacheinstance?userId='S-1-5-21-255235235-2613889227-2915372978-123456'";

HttpResponseMessage response = await client.DeleteAsync(url);

I also tried :

var downloadRequest = new HttpRequestMessage();

downloadRequest.Method = new HttpMethod("DELETE");

downloadRequest.RequestUri = new Uri(url, UriKind.RelativeOrAbsolute);

var downloadResponse = await httpClient.SendAsync(downloadRequest);

In both cases I get the 404 error, The cache instance was not found for the specified user id.

I copy the SID from the overview: https://mypiweb/piwebapi/system/cacheinstances

I am a PI Admin and use Kerberos or Basic authentication.

What am I missing? Should i do something somewhere? Some config change?

Any help appreciated.