Why Does Visual Studio Suggest a Nullable Type for a Newly Created Array in C#?

Why Does Visual Studio Type a Newly Minted Array as Nullable?

In C#, using the var keyword for variables of reference types infers a nullable reference type, as specified in the C# specification proposal. This means that for code like:

var zeroBased = new TVal[size];

Visual Studio will suggest:

TVal[]? zeroBased = new TVal[size];

The ? operator indicates that the type is potentially nullable. However, you may assume that arrays created with new are never null. Therefore, you could potentially write:

TVal[] zeroBased = new TVal[size];

So, can an array instantiated with new in C# ever return null?

Scenarios

One scenario where an array may be nullable is when it is assigned to a variable of a nullable type. For example:

TVal[]? nullableArray = new TVal[size];

In this case, the array is explicitly nullable, and its value can be set to null.

Another scenario is when using default, which creates a default value for the type. For arrays, this means an array with zero length and null elements.

TVal[]? defaultArray = default;

Therefore, it is a good practice to use the explicit type when creating arrays, especially if you are working with nullable reference types to avoid potential null values.

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