Calling the Open With dialog box from your application, using C#

This article is to introduce shell programming with C# for beginners in .NET. The Shell namespace organizes the file system and other objects managed by the Shell into a single tree-structured hierarchy. Conceptually, the Shell namespace is essentially a larger and more inclusive version of the file system. The Shell namespace objects include file system folders and files, along with "virtual" objects, such as the Recycle Bin and Printers folders. One of the primary responsibilities of the Shell is managing and providing access to the wide variety of objects that make up the system. Here, I have created a sample for demonstrating how to call the Open with dialog box in your Windows system.

Here in this article, I have developed a simple image viewer application to demonstrate the Open with dialog box in Windows, using C#. It’s really hard to explain the Shell concepts. This application is developed using Microsoft Visual C# Express Edition.
A struct-declaration consists of an optional set of attributes, followed by an optional set of struct-modifiers, followed by the keyword struct and an identifier that names the struct, followed by an optional struct-interfaces specification, followed by a struct-body, optionally followed by a semicolon. And the Serializable keyword indicates that a class can be serialized. This class cannot be inherited.

[Serializable]
public struct ShellExecuteInfo
{
public int Size;
public uint Mask;
public IntPtr hwnd;
public string Verb;
public string File;
public string Parameters;
public string Directory;
public uint Show;
public IntPtr InstApp;
public IntPtr IDList;
public string Class;
public IntPtr hkeyClass;
public uint HotKey;
public IntPtr Icon;
public IntPtr Monitor;
}
// Code For OpenWithDialog Box
[DllImport("shell32.dll", SetLastError = true)]
extern public static bool
ShellExecuteEx(ref ShellExecuteInfo lpExecInfo);
public const uint SW_NORMAL = 1;
static void OpenAs(string file)
{
ShellExecuteInfo sei = new ShellExecuteInfo();
sei.Size = Marshal.SizeOf(sei);
sei.Verb = "openas";
sei.File = file;
sei.Show = SW_NORMAL;
if (!ShellExecuteEx(ref sei))
throw new System.ComponentModel.Win32Exception();
}