Match primitive types between C# and native code

Primitive types are small value types that the runtime copies to the stack or a CPU register when you use them as function parameters or return values. You don't need to pin or otherwise manage the lifespan of primitive types when you call unmanaged functions.

C# has different names for many primitive types compared to C and other languages. For a full list of the unmanaged C types that correspond to managed C# types, refer to Platform invoke data types (Microsoft).

The following table shows the C type that some common C# types marshal to by default:

System.Int32

int

int32_t

System.Single

float

float

System.Char

char

char

System.Boolean

bool

int32_t

System.Byte

byte

unsigned char

Default marshalling is a starting point, not a guarantee. It can vary by platform and by context, such as whether the value is a parameter, a return value, or a struct field. For example, marshals to a 4-byte value by default, and marshals according to the of the call. To control the exact representation when the default isn't what you need, use

MarshalAsAttribute

(Microsoft).

Use fixed-width C types, such as from , in your unmanaged code rather than or . The size of in particular varies by platform: it's 32-bit on Windows but 64-bit on most other desktop and mobile platforms. If the managed and unmanaged code disagree about the size of a type, the data is corrupted.