Async method calling from c# get set property

Question

I have a question and want to know best practice we need to follow for async function. I have two function in my view model and they are being called from the setter of property. These two function are async void but we want to convert them to async of task as async void is a smell for bad code. But setter property does not allow us to await. So i wanted to know from where should I call these two function we also do not want to do this from the constructor as there also we can not await the fuction and contructor is not for this purpose. I just want to know the best practice to avoid calling async task function from property. I want to set and populate the data on property change so we are calling async function from property.

Answer 1

I just want to know the best practice to avoid calling async task function from property.

Simple; don't. Instead of a property, consider a method instead property getters/setters are really just regular methods that follow a convention anyway - and that convention does not and can not apply for async code.

So: instead of:

public string Something
{
    get => ???
    set => ???
}

consider:

public [async] Task<string> GetSomething() => // whatever you need here
public [async] Task SetSomething(string value) => // whatever you need here

Answer 2

As Marc already suggested, I would avoid such properties and turn them to functions, because when calling get/set of a property I expect it to be a fast and light operation which I can do very often without consequences (and an async operation indicates a more heavy operation).

Turning it to a function gives a hint to other devs, that this may come with costs. It is also possible to keep a readonly property and write a dedicated function with a good name to change it.

public int MaxLength
{
  get { return _maxLength; }
}

public async Task RestrictToMaxLength(int maxLength)
{
  await DoWhateverIsNecessary(maxLength);
  _maxLength = maxLength;
}