How to remove a users manager in AzureAD using Microsoft.Azure.ActiveDirectory.GraphClient
I managed to clear the "manager" field using the code below. It is not using the Microsoft.Azure.ActiveDirectory.GraphClient library but gets the job done.
var token = <get your adal token here>
var httpClient = new HttpClient();
httpClient.DefaultRequestHeaders.Authorization =
new AuthenticationHeaderValue("Bearer", token);
var url = "https://graph.windows.net/<tenant domain>/users/<userid>/$links/manager?api-version=1.6"
var resp = httpClient.DeleteAsync(url).Result;
if (!resp.IsSuccessStatusCode)
{
// log / throw exception etc.
}