Remove/Delete all/one item from StackExchange.Redis cache

I could not able to flush database in Azure Redis Cache, got this error:

This operation is not available unless admin mode is enabled: FLUSHDB

Instead iterate through all keys to delete:

var endpoints = connectionMultiplexer.GetEndPoints();
var server = connectionMultiplexer.GetServer(endpoints.First());
//FlushDatabase didn't work for me: got error admin mode not enabled error
//server.FlushDatabase();
var keys = server.Keys();
foreach (var key in keys)
{
  Console.WriteLine("Removing Key {0} from cache", key.ToString());
  _cache.KeyDelete(key);
}

Both answers by @Rasi and @Marc Gravell contain pieces of code needed. Based on above, here is working snippet assuming there is just 1 server:

You need to connect to redis with allowAdmin=true, one way to obtain such options is to assign AllowAdmin to already parsed string:

var options = ConfigurationOptions.Parse("server:6379");
options.AllowAdmin = true;
var redis = ConnectionMultiplexer.Connect(options);

Then to flush all databases:

var endpoints = redis.GetEndPoints();
var server = redis.GetServer(endpoints[0]);
server.FlushAllDatabases();

Above will work on any redis deployment, not just Azure.

To remove a single item:

_cache.KeyDelete(key);

To remove all involves the FLUSHDB or FLUSHALL redis command; both are available in StackExchange.Redis; but, for reasons discussed here, they are not on the IDatabase API (because: they affect servers, not logical databases).

As per the "So how do I use them?" on that page:

server.FlushDatabase(); // to wipe a single database, 0 by default
server.FlushAllDatabases(); // to wipe all databases

(quite possibly after using GetEndpoints() on the multiplexer)