您的示例缺少 T 的声明-但您已在类中对其进行了注释

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 )
    {
       ...
    }
}

在这种情况下，您可以将与预期签名匹配的任何方法(匿名或其他)传递给 getData .所以说你有一个实例

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>();

然后，任何不带参数且返回字符串的方法都可以作为该参数传递.

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);

此外，如果您有一种方法可以将数据传输到某个地方，则可以传递对其的引用

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>(); }

和

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

作为旁注，您已经声明了返回 void 的方法，但是您返回了布尔值-这对于 TryXXX 方法应该是有意义的返回一个布尔值以表示成功.

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 )
{
   ...
}

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响应您的更新:

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In response to your update:

第一个问题:通过使用TryGetOrSet方法，如何添加要缓存的项(键:userName变量，值:lastName变量)?当然，当缓存中不存在该项目时

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) ;