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Dot net core C# open photo viewer with Process Class

I am going to open the photo viewer using .net core and this is my code
using System.Diagnostics;
namespace TestProcessForOpenPhoto
{
class Program
{
static void Main(string[] args)
{
var photoViewer = new Process();
photoViewer.StartInfo.FileName = #"C:\Program Files\Windows Photo Viewer\PhotoViewer.dll";
photoViewer.StartInfo.Arguments = #" C:\Users\XXXXX\Desktop\TestImage\abc.jpg";
photoViewer.StartInfo.UseShellExecute = false;
photoViewer.Start();
}
}
}
and I got this error message
System.ComponentModel.Win32Exception: 'The specified executable is not a valid application for this OS platform.'
Can anyone help me to fix this bug, thanks

After researching this I noticed folks using rundll32.exe to execute an export from PhotoViewer.dll to display a picture using Microsoft Photo Viewer application. So I think that's what OP was trying to do, they just forgot to use the rundll32.exe application.
So I thought I'd take a crack at this and not use the rundll32.exe and just call the export directly. I debugged it with x86dbg and saw that it's passing in 4 parameters: pointer, pointer, pointer (to wchar_t*), int. I don't know what the parameters do, so I just set them to NULL and made sure to pass in the path to the picture as the 3rd and it seems to work.
So this will do what you want it to do. I know that hard-coding system paths is bad practice, but maybe someone who has more time can make this more dynamic.
private static class WindowsPhotoViewer
{
private const string FilePath32 = #"c:\program files (x86)\Windows Photo Viewer\PhotoViewer.dll";
private const string FilePath64 = #"c:\program files\Windows Photo Viewer\PhotoViewer.dll";
[DllImport(FilePath32, CharSet = CharSet.Unicode, EntryPoint = "ImageView_FullscreenW")]
private static extern void ImageView_Fullscreen32(
IntPtr unknown1, IntPtr unknown2, string path, int unknown3);
[DllImport(FilePath64, CharSet = CharSet.Unicode, EntryPoint = "ImageView_FullscreenW")]
private static extern void ImageView_Fullscreen64(
IntPtr unknown1, IntPtr unknown2, string path, int unknown3);
public static bool ShowImage(FileInfo imageFile)
{
if ((IntPtr.Size == 8) && File.Exists(FilePath64) && imageFile.Exists)
{
ImageView_Fullscreen64(IntPtr.Zero, IntPtr.Zero, imageFile.FullName, 0);
return true;
}
else if ((IntPtr.Size == 4) && File.Exists(FilePath32) && imageFile.Exists)
{
ImageView_Fullscreen32(IntPtr.Zero, IntPtr.Zero, imageFile.FullName, 0);
return true;
}
return false;
}
}
Then you can call it as so:
if(!WindowsPhotoViewer.ShowImage(new FileInfo(#"c:\users\andy\desktop\test.jpg")))
{
Console.WriteLine("Failed to show image");
}

Error when trying to replace an UNC path by a string

Sorry for some maybe very basic questions. I simply wanted to replace the UNC path by a string. These lines with the UNC path for a C++ connection perfectly works:
[DllImport(C:\\Users\\SJ\\Documents\\VS2015\\Projects\\P_01\\Debug\\EV_01.dll",
EntryPoint = "DDentry", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
public static extern void DDentry
(
[MarshalAs(UnmanagedType.SafeArray, SafeArraySubType = VarEnum.VT_BSTR)]
string[,] pArrayStr
);
Replacing the UNC path by a string gives an error "An object reference is required for the non-static field, method, or property"
string UNCpath = #"C:\\Users\\SJ\\Documents\\VS2015\\Projects\\P_01\\Debug\\EV_01.dll";
[DllImport(UNCpath,
EntryPoint = "DDentry", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
public static extern void DDentry
(
[MarshalAs(UnmanagedType.SafeArray, SafeArraySubType = VarEnum.VT_BSTR)]
string[,] pArrayStr
);
Many thank for your ideas ..

You cannot pass the instance value UNCPath into an attribute like that. It would need to be a constant. Also, if you use the double-backslash escape sequences, you can't use the # prefix to the string.
Try this:
const string UNCpath = "C:\\Users\\SJ\\Documents\\VS2015\\Projects\\P_01\\Debug\\EV_01.dll";
[DllImport(UNCpath,
EntryPoint = "DDentry", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
public static extern void DDentry
(
[MarshalAs(UnmanagedType.SafeArray, SafeArraySubType = VarEnum.VT_BSTR)]
string[,] pArrayStr
);

You are trying to use a non-constant string with an attribute and it isn't allowed. You must declare your string as "const".

How to shorten a path in c# and keep it valid

I work in a place where directories have such a looong name and are in such a looong tree.
And I'm having problems with too long path names for folders in an external applicatoin (I can't change this external application, but I can give it shortened path names).
I know Microsoft operating systems can shorten path names such as transforming C:\TooLongName\TooLongSubDirectory in something like C:\TooLon~1\TooLon~1.
But how can I do this in C# and still keep the nave valid and usable?
PS: I'm not using the standard FileInfo and DirectoryInfo classes, I'm using just strings that will be sent to an external application that I cannot change in any way.

If you are unable to use the long path support build into Windows 10 you are able to use the Win32 command GetShortPathName . In order to generate a suitable path.
class Program
{
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern uint GetShortPathName(
[MarshalAs(UnmanagedType.LPTStr)]
string lpszLongPath,
[MarshalAs(UnmanagedType.LPTStr)]
StringBuilder lpszShortPath,
uint cchBuffer);
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern uint GetShortPathName(string lpszLongPath, char[] lpszShortPath, int cchBuffer);
static void Main(string[] args)
{
StringBuilder builder = new StringBuilder(260);
var shortPath = GetShortPathName(#"C:\Projects\Databases\ReallllllllllllllyLOOOOOOOOOOOOOOOOOOOOOONGPATHHHHHHHHHHH\StillllllllllllllllllGOoooooooooooooooooooooooing", builder, (uint)builder.Capacity);
Console.WriteLine(builder.ToString());
Console.ReadKey();
}
}
Produces C:\Projects\DATABA~1\REALLL~1\STILLL~1

WPF application file association: DefaultIcon is not working

I want to association ".abc" file to my WPF application.
I add the association using this code:
public class FileAssociation
{
static RegistryKey Root
{
get
{
return Registry.CurrentUser;
}
}
// Associate file extension with progID, description, icon and application
public static void Associate(string extension,
string progID, string description, string application)
{
Require.NotNullOrEmpty(extension, "extension");
Require.NotNullOrEmpty(progID, "progID");
Require.NotNullOrEmpty(application, "application");
Require.NotNullOrEmpty(description, "description");
Root.CreateSubKey(extension).SetValue("", progID);
using (var key = Root.CreateSubKey(progID))
{
key.SetValue("", description);
key.CreateSubKey("DefaultIcon").SetValue("", ToShortPathName(application).Quote() + ",0");
key.CreateSubKey(#"Shell\Open\Command").SetValue("", ToShortPathName(application).Quote() + " \"%1\"");
// Tell explorer the file association has been changed
SHChangeNotify(0x08000000, 0x0000, IntPtr.Zero, IntPtr.Zero);
}
}
// Return true if extension already associated in registry
public static bool IsAssociated(string extension)
{
return (Root.OpenSubKey(extension, false) != null);
}
[DllImport("shell32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern void SHChangeNotify(uint wEventId, uint uFlags, IntPtr dwItem1, IntPtr dwItem2);
[DllImport("Kernel32.dll")]
private static extern uint GetShortPathName(string lpszLongPath,
[Out] StringBuilder lpszShortPath, uint cchBuffer);
// Return short path format of a file name
private static string ToShortPathName(string longName)
{
StringBuilder s = new StringBuilder(1000);
uint iSize = (uint)s.Capacity;
uint iRet = GetShortPathName(longName, s, iSize);
return s.ToString();
}
}
Note: The Quote() extension method is used just to make string abc to "abc".
Now the file association works fine! I can double click the ".abc" files to open my WPF app.
But the DefaultIcon is not working. The DefaultIcon Registery key is set to "D:\path\to\MyWPFApp.exe",0. The application icon of my WPF app is set to an icon in the properties page (I can see that the icon of MyWPFApp.exe is already changed). What's wrong? Thanks!
BTW: I'm using .NET 4 in Windows 8

You don't need the DefaultIcon entry. The first icon is used by default.
remove it and it should work ^^
If I remove the ToShortPathName (long name is ok with quotes) and
change the Root property returns Registry.ClassesRoot the code works here.

Set DllImport attribute dynamically

I am making use of an external unmanaged dll using PInvoke and the DllImport attribute. eg.
[DllImport("mcs_apiD.dll", CharSet = CharSet.Auto)]
private static extern byte start_api(byte pid, byte stat, byte dbg, byte ka);
I am wondering if it is possible to alter the dll file details (mcs_apiD.dll in this example) dynmically in some manner, if for instance I wanted to build against another dll version

Yes this is possible, you'll have to do part of the job that the P/Invoke marshaller does. Loading the DLL and finding the entry point of the exported function. Start by declaring a delegate whose signature matches the exported function:
private delegate byte start_api(byte pid, byte stat, byte dbg, byte ka);
Then use code like this:
using System.ComponentModel;
using System.Runtime.InteropServices;
...
static IntPtr dllHandle;
...
if (dllHandle == IntPtr.Zero) {
dllHandle = LoadLibrary("mcs_apiD.dll");
if (dllHandle == IntPtr.Zero) throw new Win32Exception();
}
IntPtr addr = GetProcAddress(dllHandle, "_start_api#16");
if (addr == IntPtr.Zero) throw new Win32Exception();
var func = (start_api)Marshal.GetDelegateForFunctionPointer(addr, typeof(start_api));
var retval = func(1, 2, 3, 4);
...
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr LoadLibrary(string name);
[DllImport("kernel32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
private static extern IntPtr GetProcAddress(IntPtr hModule, string name);
Lots of ways to get this wrong of course. Do note that you have to use the actual exported name from the DLL, you no longer get the help from the P/Invoke marshaller to help with name decoration. Use dumpbin.exe /exports on the DLL if you are not sure what the export name looks like.

you can't change the name of the dll but you can alter the path of the library being loaded (like by reading it from the registry or a configuration file) and load it manually with LoadLibrary kernel32's function: see my answer there.