serviceprovider, cache etc. finished generics but cast

i'm articulate c# 3.5 3.0.
i know cache serviceprovider have wholly instance whole application. box serviceprovider feeling this

public stationary category service<t>
{
    open stationary t value {get; set;}
}

and used opposite forms this:

service<idbconnection>.value = new sqlconnection("...");
service<idesigner>.value = ...;
//...
idbcommand cmd = service<idbconnection>.value.createcommand();

static cache also easy:

public stationary category cache<t>
{
    private stationary dictionary<int, t> cache = new dictionary<int, t>();

    open stationary vacant add(int key, t value)
    {
        cache.add(key, value);
    }

    open stationary t find(int key)
    {
        relapse cache[key];
    }
}

and used this:

cache<string>.add(1, "test");
cache<datetime>.add(2, datetime.now);
//...
string found = cache<string>.find(1);

my doubt is: i emanate similiar cache use provider i wish have 2 some-more opposite instances each. here instance code, i wish use provider:

serviceprovider provider = new serviceprovider();
provider.add<idbconnection>(new sqlconnection("..."));
provider.add<idesigner>(...);
//...
serviceprovider provider1 = new serviceprovider();
provider1.add<idbconnection>(new sqlconnection("..."));
//...
//...
idbcommand cmd1 = provider.getservice<idbconnection>().createcommand();
idbcommand cmd2 = provider1.getservice<idbconnection>().createcommand();

the wholly doing i have conduct controlling casting i wish avoid.

public category serviceprovider
{
    private dictionary<type, object> services = new dictionary<type, object>();
    open vacant add<t>(t value)
    {
        services.add(typeof(t), value);
    }

    open t getservice<t>()
    {
        relapse (t) services[typeof (t)];
    }
}