How pass Func to method parameter

Question

I have found code for Get/Set cache item, but I don\'t know how I can call this method, eg. how pass proper Func getData to this method?

Answer 1

Your example is missing the declaration of T - but you've commented its on the class

public class Cache<T>
{
    public void TryGetOrSet( string cacheKey, Func<T> getData, out T returnData, CacheItemPolicy policy = null )
    {
       ...
    }
}

In this case, you can pass to getData any method (anonymous or otherwise) which matches the signature expected. So say you have an instance

var myCache = new Cache<string>();

Then any method which takes no parameters and returns a string can be passed as that parameter.

string value = null;
myCache.TryGetOrSet("some_key", () => "foo", out value);

Also if you have a method which gets your data somewhere a reference to that can be passed

// somewhere eg "MyRepository"
public IEnumerable<MyObject> MyDataAccessMethod() { return Enumerable.Empty<MyObject>(); }

and

var myCache = new Cache<IEnumerable<MyObject>>();
var repo = new MyRepository();
IEnumerable<MyObject> data = null;
myCache.TryGetOrSet("some_key", repo.MyDataAccessMethod, out data);

As a side note, you've declared the method to return void but youre returning a boolean - this makes sense as a TryXXX method should return a boolean to indicate success.

public bool TryGetOrSet( string cacheKey, Func<T> getData, out T returnData, CacheItemPolicy policy = null )
{
   ...
}

---

In response to your update:

First question: By using method TryGetOrSet how I can add item (key : userName variable, value: lastName variable) to cache? Of course when this item doesn't exists in cache

var cache = new Cache<string>("UserInfo");
var userName = "test";
var lastName = "test2";
string result = null;
TryGetOrSet(userName, () => lastName, out result) ;