There is no built-in method to list all items in the cache.
You're correct, it's possible to list all items using GetObjectsInRegion for a named cache. You have to know first all regions names (if used) or call GetSystemRegions to get all (default) system regions. A simple foreach will allow you to list all items. When you put something into the cache without region name, it will be added to a system region.
Here is a basic example
// Declare array for cache host(s).
DataCacheServerEndpoint[] servers = new DataCacheServerEndpoint[1];
servers[0] = new DataCacheServerEndpoint("YOURSERVERHERE", 22233);
// Setup the DataCacheFactory configuration.
DataCacheFactoryConfiguration factoryConfig = new DataCacheFactoryConfiguration();
factoryConfig.Servers = servers;
factoryConfig.SecurityProperties = new DataCacheSecurity(DataCacheSecurityMode.None, DataCacheProtectionLevel.None);
// Create a configured DataCacheFactory object.
DataCacheFactory mycacheFactory = new DataCacheFactory(factoryConfig);
// Get a cache client for the default cache
DataCache myCache = mycacheFactory.GetDefaultCache(); //or change to mycacheFactory.GetCache(myNamedCache);
//inserty dummytest data
myCache.Put("key1", "myobject1");
myCache.Put("key2", "myobject2");
myCache.Put("key3", "myobject3");
Random random = new Random();
//list all items in the cache : important part
foreach (string region in myCache.GetSystemRegions())
{
foreach (var kvp in myCache.GetObjectsInRegion(region))
{
Console.WriteLine("data item ('{0}','{1}') in region {2} of cache {3}", kvp.Key, kvp.Value.ToString(), region, "default");
}
}