Your c# example for https://graph.microsoft.com/v1.0/me/people?$search="jesper"
GraphServiceClient graphClient = new GraphServiceClient( authProvider );
var people = await graphClient.Me.People
.Request()
.Search("jesper")
.GetAsync();
Error I'm getting:
not sure if this is meant to happen but seems wrong that you cant use the search function https://developer.microsoft.com/en-us/graph/graph-explorer
