# ArrayElementAsRef<T>(void*, int)

> Obtains a reference to a value of type T in an array at a specified index in memory.

## Definition

* **Type:** Method
* **Namespace:** [Unity.Collections.LowLevel.Unsafe](/engine/6000.3/script-reference/unity/collections/lowlevel/unsafe.md)
* **Assembly:** UnityEngine.CoreModule

```csharp
public static ref T ArrayElementAsRef<T>(void* ptr, int index) where T : struct
```

### Parameters

**** (\[void\*]\(https\://learn.microsoft.com/dotnet/api/system.void)): A pointer to the first element of the array. Ensure that this pointer is valid and points to allocated memory.**** (\[int]\(https\://learn.microsoft.com/dotnet/api/system.int32)): The zero-based index of the element to reference. Verify that the index is within the bounds of the array to prevent access violations.

### Returns

| Type | Description                                                                                                                                                |
| ---- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- |
| T    | A reference to the value of type T at the specified index within the array. This reference allows direct manipulation of the value at its memory location. |

### Remarks

The `ArrayElementAsRef` method allows direct access to an array element by its index in memory. This method provides a reference to the element, enabling efficient data manipulation without copying. Use this method with care, as incorrect pointer usage can cause memory corruption or application crashes.

```csharp
using UnityEngine;
using Unity.Collections.LowLevel.Unsafe;
using System.Runtime.InteropServices;

public class ArrayElementAsRefExample : MonoBehaviour
{
    [StructLayout(LayoutKind.Sequential)]
    struct CustomStruct
    {
        public int Id;
        public float Value;
    }

    void Start()
    {
        int arrayLength = 5;

        // Allocate a buffer for CustomStruct using stackalloc
        unsafe
        {
            CustomStruct* structArray = stackalloc CustomStruct[arrayLength];

            // Initialize the array with values
            for (int i = 0; i < arrayLength; i++)
            {
                structArray[i].Id = i;
                structArray[i].Value = i * 1.5f;
            }

            // Get a reference to an element using ArrayElementAsRef
            ref CustomStruct element = ref UnsafeUtility.ArrayElementAsRef<CustomStruct>(structArray, 2);
            element.Value = 99.9f;  // Modify the value in place

            // Output the modified value
            Debug.Log($"Modified element at index 2: Id = {structArray[2].Id}, Value = {structArray[2].Value}");
        }
    }
}
```

Additional Resources: [UnsafeUtility.ReadArrayElement](/engine/6000.3/script-reference/unity/collections/lowlevel/unsafe/unsafeutility/readarrayelement.md), [UnsafeUtility.WriteArrayElement](/engine/6000.3/script-reference/unity/collections/lowlevel/unsafe/unsafeutility/writearrayelement.md).