LazyAction in C#?

Question

Is there a way in the C# standard API to lazily initialize a block of code?

I know Lazy<T> but it is meant to initialize one variable, and requires a function that returns a T. I'd like something that's more like a LazyAction.

private _lazyInit = new LazyAction( () => {
    ...
    // Do something big like get some data from DB
    ...
    _myField1 = ...
    _myField2 = ...
    ...
    do no return stuff.
}

public object get_Field1() { _lazyInit.EnsureDone(); return _myfield1; }
public object get_Field2() { _lazyInit.EnsureDone(); return _myfield2; }

For thread-safety, the LazyAction would have some mechanism to ensure it's only run once.

Answer 1

Although I like Jeroen Mostert's proposal better, you could do something like this:

create a class that holds your initialization method:

class LazyInitializer
{
    private readonly Action initFunc;

    class State { public bool Initialized = false; }

    public LazyInitializer(Action initFunc)
    {
        this.initFunc = initFunc;
    }

    public Action CreateInitializer()
    {
        var state = new State();

        return () =>
        {
            lock (state)
            {
                if (state.Initialized == false)
                {
                    initFunc();
                    state.Initialized = true;
                }
            }
        };
    }
}

and then use it like:

var lazyInit = new LazyInitializer(() =>
{
    //here your initialization code
    ...
    _myField1 = ...
    _myField2 = ...
    ...
});

//Create the initializer action
var initialize = lazyInit.CreateInitializer();

//use it like:
public object get_Field1() { initialize(); return _myfield1; }
public object get_Field2() { initialize(); return _myfield2; }