8/13/2019 2555A_05

1/16

Module 5:Interoperating with

Managed Objects

8/13/2019 2555A_05

2/16

Overview

Using .NET and COM Components in a Windows FormsApplication

Calling Win32 APIs from Windows Forms Applications

8/13/2019 2555A_05

3/16

Lesson: Using .NET and COM Components in aWindows Forms Application

COM vs .NET

How to Call COM Components from .NET

Role of the RCW How to Generate Interop Assemblies

Private, Shared, and Primary Interop Assemblies

Practice: Using COM Components in .NET-BasedApplications

8/13/2019 2555A_05

4/16

COM vs .NET

COM Model .NET Framework Model

Interface based Object based

GUIDs Strong names

Binary standard Type standard

Type library Metadata

HResults Exceptions

Reference counting Garbage collection

Immutable Resilient

8/13/2019 2555A_05

5/16

How to Call COM Components from .NET

The CLR enables managed code to call COM objectsthrough a proxy called the Runtime Callable Wrapper(RCW)

The RCW is a managed object and subject to garbagecollection

COM Object A

COM Object B

RCW

RCW

.NET Client

.NET Client

Unmanaged Managed

http://localhost/var/www/apps/conversion/tmp/scratch_9/2555A_05A005.htm

8/13/2019 2555A_05

6/16

Role of the RCW

Maintains object lifetime

Marshals method calls between managed andunmanaged code

Consumes selected COM interfaces without exposing

them to the .NET client

COM

Object RCW.NET

Client

Unmanaged Managed

INew

IUnknown

IDispatch

INew

8/13/2019 2555A_05

7/16

How to Generate Interop Assemblies

Unmanaged Managed

Interop

Assembly

A

B

C

D

Tlbimp.exe

A B

C D

COM object

COM object

8/13/2019 2555A_05

8/16

Private, Shared, and Primary Interop Assemblies

Application1.exe

Metadata

MSIL

C:\Application1

Productlib.dll

Metadata

Application2.exe

Metadata

MSIL

C:\Application2

Productlib.dll

MetadataPrivate Interop

Assemblies

Productlib.dll

MetadataGAC

Strong Named

Assemblies

Primary Interop Assembly is an assembly signed by thecompany that produced the original type library

8/13/2019 2555A_05

9/16

Practice: Using COM Components in .NET-BasedApplications

In this practice, you will

Register the COM Component

Add reference to the COM component

Add code to use the COM component in a.NET-based application

Begin reviewing the objectives

for this practice activity15 min

8/13/2019 2555A_05

10/16

Lesson: Calling Win32 APIs from Windows FormsApplications

Platform Invocation Services

How to Define Functions by Using the DllImportAttribute

How to Call Win32 APIs from a Windows FormsApplication

Practice: Calling Win32 APIs

8/13/2019 2555A_05

11/16

Platform Invocation Services

A platform invoke call to an unmanaged DLL function

The PInvoke Model

Unmanaged Managed

Standard

marshaling service

DLL

DLL

function

Platform

invoke

Common languageruntime

Assembly

Metadata

IL code

CompilerManaged

source

code

8/13/2019 2555A_05

12/16

How to Define Functions by Using the DllImportAttribute

DllImport attribute is used to define functions

Parameters are used to specify specific behavior

CallingConvention

CharSet

[DllImport("KERNEL32.DLL", EntryPoint="MoveFileW",SetLastError=true,

CharSet=CharSet.Unicode, ExactSpelling=true,

CallingConvention=CallingConvention.StdCall)]

public static extern bool MoveFile(String src, Stringdst);

EntryPoint

ExactSpelling

8/13/2019 2555A_05

13/16

How to Call Win32 APIs from a Windows FormsApplication

Create a new project in Visual Studio .NET

Import the System.Runtime.InteropServices namespace

using System.Runtime.InteropServices;

Define a function using DllImport

Add code to call the Win32 API from a Windows Form

bool result;System.IntPtr resourceHandle = System.IntPtr.Zero;result =

Win32PlaySoundClass.PlaySound_DllImport(soundFileName,resourceHandle,0);

Determine the details of the function you want to call

8/13/2019 2555A_05

14/16

Practice: Calling Win32 APIs

Begin reviewing the objectives

for this practice activity15 min

In this practice, you will call a Win32 API froma .NET-based application using the DllImport

attribute

8/13/2019 2555A_05

15/16

Review

Using .NET and COM Components in a WindowsForms Application

Calling Win32 APIs from Windows Forms Applications

8/13/2019 2555A_05

16/16

Lab 5.1: Interoperating with COM and Calling Win32APIs

Exercise 1: Using a COM Component in a.NET-Based Application

Exercise 2:Calling Win32 APIs from a.NET-Based Application