Freezable/Immutable property

[CodingOctocat]

I don't know how implement the "Freezable/Immutable" property, but it would be simple to add a language feature that would accomplish this:

public class MyClass
{
    public Foo MyFoo { get; freez; }

    public void Do()
    {
        MyFoo.Property1 = xxx; // Ok
    }
}

var cls = new MyClass();
cls.MyFoo = new MyFoo(); // Error
cls.MyFoo.Property1 = xxx; // Error
cls.MyFoo.Property1.SubProperty1 = xxx; // Error
cls.MyFoo.ListProperty[0] = xxx; // Error

Possible syntax:

public Foo MyFoo { get; freez; }
public freez Foo MyFoo { get; }

public Foo MyFoo { get; private freez;} // Debatable
public freez Foo MyFoo { get; private set; }

// Filed support
public freez Foo MyFoo;

[HaloFour]

Don't add a set accessor, or make it an init accessor if you want it mutable during initialization.

[huoyaoyuan]

This does not provide deep immutability though.

[HaloFour]

No, but I don't see how this proposal would either. A keyword on a property wouldn't prevent you from passing it's value by reference to some arbitrary method that would be totally unaware of that restriction.

[CodingOctocat]

Perhaps only deep clones can be used at this stage? Is there any other more elegant way, such as a proxy like Freezable<Foo>/Immutable<Foo>.

private Foo _myFoo;
public Foo MyFoo => _myFoo.DeepClone()