Calling a DLL Function

Although calling unmanaged DLL functions is nearly identical to calling other managed code, there are differences that can make DLL functions seem confusing at first. This section describes some of the unusual calling-related issues.

Structures that are returned from platform invoke calls must be data types that have the same representation in managed and unmanaged code. Such structures are called blittable types because they do not require conversion (see Blittable and Non-Blittable Types). To call a function that has a non-blittable structure as its return type, you can define a blittable helper type of the same size as the non-blittable type and convert the data after the function returns.

In This Section

• Passing Structures
  Identifies the issues of passing data structures with a predefined layout.

• Callback Functions
  Provides basic information about callback functions.

• How to: Implement Callback Functions
  Describes how to implement callback functions in managed code.

Related Sections

• Consuming Unmanaged DLL Functions
  Describes how to call unmanaged DLL functions using platform invoke.

• Marshaling Data with Platform Invoke
  Describes how to declare method parameters and pass arguments to functions exported by unmanaged libraries.

Change History

Date	History	Reason
February 2010	Clarified that return types must be blittable.	Customer feedback.