passing-arrays-using-ref-and-out.md

title	Passing Arrays Using ref and out (C# Programming Guide)
ms.date	07/20/2015
ms.prod	.net
ms.technology	devlang-csharp
ms.topic	article
helpviewer_keywords	arrays [C#], passing using ref and out
ms.assetid	6a2b261e-a1cc-49a6-b4f0-6cacae385a1e
caps.latest.revision	16
author	BillWagner
ms.author	wiwagn

Passing Arrays Using ref and out (C# Programming Guide)

Like all out parameters, an out parameter of an array type must be assigned before it is used; that is, it must be assigned by the callee. For example:

[!code-csharpcsProgGuideArrays#39]

Like all ref parameters, a ref parameter of an array type must be definitely assigned by the caller. Therefore, there is no need to be definitely assigned by the callee. A ref parameter of an array type may be altered as a result of the call. For example, the array can be assigned the null value or can be initialized to a different array. For example:

[!code-csharpcsProgGuideArrays#40]

The following two examples demonstrate the difference between out and ref when used in passing arrays to methods.

Example

In this example, the array theArray is declared in the caller (the Main method), and initialized in the FillArray method. Then, the array elements are returned to the caller and displayed.

[!code-csharpcsProgGuideArrays#37]

Example

In this example, the array theArray is initialized in the caller (the Main method), and passed to the FillArray method by using the ref parameter. Some of the array elements are updated in the FillArray method. Then, the array elements are returned to the caller and displayed.

[!code-csharpcsProgGuideArrays#38]

See Also

ref
out parameter modifier
C# Programming Guide
Arrays
Single-Dimensional Arrays
Multidimensional Arrays
Jagged Arrays