> For the complete documentation index, see [llms.txt](https://netick.gitbook.io/v1/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://netick.gitbook.io/v1/change-callback.md).

# Change Callback

## For Properties

You can have a method get called whenever a networked property changes, which is very useful. To do that, add the attribute `[OnChanged]` to the method and give it the name of the property. The method must have one parameter of the same type of the property which would contain its previous value.

Example:

```csharp
[Networked]
public int Health { get; set; }

[OnChanged(nameof(Health ))]
private void OnHealthChanged(int previous)
{
        // Something that happens when the Health property changes
}
```

## **For Arrays**

If you have an array and want a callback for when an element changes, you can do so as follows:

Example:

```csharp
[Networked(size: 10)]
public NetworkArray<int> Items { get; set; }

[OnChanged(nameof(Items))]
private void ArrayChanged(int index)
{
      // Something that happens when an element of the array changes
}
```

The difference here to a variable property is that the callback method must have an index parameter that points to the changed element.


---

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