Develop Reference

Null Reference Exception when calling iText7 PdfAcroForm.GetAcroForm() in .Net Core 3.1 class library

I am working on converting an application to .Net Core 3.1, and in my class library I am generating a PDF form from an existing template, and filling that form with data. In ITextSharp, the predecessor to IText7, the PdfAcroForm static method ".GetAcroForm()" worked perfectly, but in the current version of iText7 (7.1.12) a Null Reference Exception is thrown. I have followed the documentation to the best of my ability, but I am unsure how to continue. Any suggestions would be appreciated.
NOTE: The template path exists, the new document shows that it has been filled properly, and it is impossible to "new" a PdfAcroForm, you are required to use the static .GetAcroForm() method.
A null check will not solve this issue, as the object should never be null. The documentation indicates that the .GetAcroForm() method will create a new form if the parameter "createNotExist" is set to true, which I have done here.
I have researched and have located an issue on the iText GitHub that indicates that this issue was "fixed" around a year ago: https://github.com/itext/itext7/pull/44#issue-351612749
The following is the method which prepares the forms:
public string DocumentGenerator(string templatePath, FormFieldSet[] formFieldSet, bool useSpecailOutputPath)
{
if(!File.Exists(templatePath))
{
throw new Exception("The template file provided does not exist: MC-071(iText)");
}
string newFile = useSpecailOutputPath ?
m_SpecialOutputPath :
Path.GetTempPath() + Guid.NewGuid().ToString() + ".pdf";
try
{
PdfDocument newDocument = new PdfDocument(new PdfReader(templatePath), new PdfWriter(newFile));
PdfAcroForm acroForm = PdfAcroForm.GetAcroForm(newDocument, true); // <=== Exception Thrown Here
foreach (FormFieldSet fs in formFieldSet)
{
acroForm.GetField(fs.FieldName).SetValue(fs.FillValue);
}
// Sets form flattening
acroForm.FlattenFields();
// Closes and writes the form
newDocument.Close();
return newFile;
}
catch { return string.Empty; };
}
Any suggestions would be greatly appreciated

I had the same problem, and after digging down all the way to iText7's internal objects and methods, I finally "solved" my problem.
Apparently iText has some internal errors/exceptions that they are just sort of "skipping" and "pushing past", because I realized by accident that I had "Enable Just My Code" in Visual Studios disabled, and so my system was trying to debug iText7's code as well as mine. The moment that I re-enabled it in my Visual Studio settings (Tools > Options > Debugging > General > Enable Just My Code checkbox), the problem magically went away.
So I spent four hours trying to troubleshoot a problem that was in THEIR code, but that they apparently found some way to work around and push through the method anyways even on a null reference failure.
My convert to PDF function is now working just fine.

Just an update to anyone looking for this issue. This is a known issue and is fixed in the current development branch. You are safe to bypass the exception in visual studio until it is corrected. This has no negative impact on the functionality and is the result of a misplaced return in the original iText7 source.

How can I get for reading and writing Properties.Settings.Default.UpgradeRequired property?

In my WPF MVVM application I need to check if my application runs first after its installation. I had reviewed some examples in SO and in one of them - how to check whether my c# window app is running first time after installation I found the following code where the author recommended the use of UpgradeRequired:
// this must happen as soon as your program starts, before
// you do anything else with the settings
if (Properties.Settings.Default.UpgradeRequired)
{
// upgrade FIRST, before doing anything else with the settings
Properties.Settings.Default.Upgrade();
Properties.Settings.Default.UpgradeRequired = false;
Properties.Settings.Default.Save();
}
I quote here his words: "I also suggest adding a "UpgradeRequired" boolean to the settings which is by default true...." But when I try to add the same code in my App.xaml.cs file in OnStartUp event handler then the following error occured: "Settings does not contain a definition for UpgradeRequired" and UpgradeRequired was underlined with a red wavy line. I havn't faced with Properties.Settings before. So I'd like to know: Which assembly reference I should add to my application? What must I do to get access to Properties.Settings.Default.UpgradeRequired? our help would be greatly appreciated.

This not in any Assembly it's your oun custom settings. It's all explained here https://msdn.microsoft.com/en-us/library/a65txexh(v=vs.140).aspx

MagneticStripeReader.GetDefaultAsync(); returns null

I have a usb connected MSR reader and i am trying to get it by using the sample codes proveded in here. This works fine but the problem is when i add the same code to my app it doesn't work. GetDefaultAsync returns null.
private static MagneticStripeReader _reader = null;
public static async void StartRead()
{
if (await CreateDefaultMagneticStripeReaderObject())
{
....
}
}
private static async Task<bool> CreateDefaultMagneticStripeReaderObject()
{
if (_reader == null)
{
_reader = await MagneticStripeReader.GetDefaultAsync();
if (_reader == null)
return false;
}
return true;
}
My code is like above, very similer to sample but it doesnt work. Also i've added the device capability of pointOfService. So that is not the case.

I was in the exact same situation and I spent the last 5 hours, finally I know what was going on. You are missing a capability in the Package.appxmanifest
'pointOfService' is the capability you want to include. This capability does not show in the UI and therefore I could not find any difference between my broken project and Microsoft's sample project. You can not add that capability using the UI. You have to manually add it by modifying the XML file.
The sample project by Microsoft have it too
https://github.com/Microsoft/Windows-universal-samples/blob/master/Samples/MagneticStripeReader/cs/Package.appxmanifest#L53

Make sure the card reader is in HID mode and not Keyboard emulation mode. That was one of my problems.
To do this is really wonky. MagTek has a ActiveX control on their website to assist us... because ActiveX is awful, you can only use it with InternetExplorer (it won't even work with Edge.)
go here in IE: https://www.magtek.com/changemode/
Enable active X when it pops up, and you can change from hid to keyboard and back.

C# - Load existing system environment variables when the current process don't have them loaded

On Windows, I have a C# assembly that is COM visible. It references other assemblies to control an application in the machine. It works fine.
However, under Apache Web Server and using CGI, it doesn't work. After doing some debuging, I found out that the problem is that, while running under Apache's CGI, the environment variables SYSTEMROOT and SYSTEMDRIVE, which aparently are needed by the referenced assemblies, are not loaded.
I can configure Apache to pass those environemtn variables too, but before doing so, I'd really like to know if there's some command I can put on my C# COM visible assembly to make it load environment variables as if it was, let's say, the SYSTEM user or something like that, so it doesn't have to relay on the environment passed by the starting application.
How do you force loading an existent system environment variable in C#, when IT IS NOT SET in the current process (or it was process-deleted by the launching process)?
Thanks in advance for any suggestions!
EDIT 1 - ADDED INFO: Just to make it more clear (as I see in the current answers it's not so clear): Apache intendedly deletes a lot of environment variables for CGI processes. It's not that Apache cannot see them, it can, but it won't pass them to CGI processes.

This should do the trick:
Environment.GetEnvironmentVariable("variable", EnvironmentVariableTarget.Machine);
I did a small test and it is working:
//has the value
string a = Environment.GetEnvironmentVariable("TMP");
Environment.SetEnvironmentVariable("TMP", null);
//does not have has the value
a = Environment.GetEnvironmentVariable("TMP");
//has the value
a = Environment.GetEnvironmentVariable("TMP", EnvironmentVariableTarget.Machine);

SOLUTION: Marco's answer was great and technically answered my question - except that I found out that the environment variables SYSTEMROOT and SYSTEMDRIVE are not really set in the registry where all environment variables are set, so, the chosen answer works for all variables except those two, which I specified in the OP.
SYSTEMROOT is defined on the registry in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRoot, and apparently (after more research), SYSTEMDRIVE is generated as a substring of SYSTEMDRIVE.
So, to get SYSTEMDRIVE and SYSTEMROOT from registry and load them into the environment:
using Microsoft.Win32;
namespace MySpace
{
public class Setup
{
public Setup()
{
SetUpEnvironment();
}
private void SetUpEnvironment()
{
string test_a = Environment.GetEnvironmentVariable("SYSTEMDRIVE", EnvironmentVariableTarget.Process);
string test_b = Environment.GetEnvironmentVariable("SYSTEMROOT", EnvironmentVariableTarget.Process);
if (test_a == null || test_a.Length == 0 || test_b == null || test_b.Length == 0)
{
string RegistryPath = "HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
string SYSTEMROOT = (string) Registry.GetValue(RegistryPath, "SystemRoot", null);
if (SYSTEMROOT == null)
{
throw new System.ApplicationException("Cannot access registry key " + RegistryPath);
}
string SYSTEMDRIVE = SYSTEMROOT.Substring(0, SYSTEMROOT.IndexOf(':') + 1);
Environment.SetEnvironmentVariable("SYSTEMROOT", SYSTEMROOT, EnvironmentVariableTarget.Process);
Environment.SetEnvironmentVariable("SYSTEMDRIVE", SYSTEMDRIVE, EnvironmentVariableTarget.Process);
}
}
}
}
Then you can just call Setup setup = new Setup(); from other classes. And that's it. :-)

Environment.GetEnvironmentVariable
see reference here.
e.g.
Environment.CurrentDirectory = Environment.GetEnvironmentVariable("windir");
DirectoryInfo info = new DirectoryInfo(".");
lock(info)
{
Console.WriteLine("Directory Info: "+info.FullName);
}

Are the variables set as system wide?
If they are not, that is what you need to do, otherwise create user variables for the user the COM is running under.

Thank you. I cannot state with any certainty that this has once and for all driven a stake through the heart of the vampire, but amazingly enough, the error has disappeared (for now). The odd thing is that access to the statement
Environment.GetEnvironmentVariable("variable", EnvironmentVariableTarget.Machine);
is a real oddity in the debugger. It does not show up in Intellisense and does not even appear to fire, which leads me to suspect, which you all knew already, that this is some sort of magic runtime object Environment that has no instantiation in the debugger but also can be benignly jumped over. Oh well.
Oh and I should mention that after you see that error, you will note oddities in your Windows OS, which is worrisome. In particular, you will see, if you try to use the Control Panel /System/Advanced Properties (whatever) that it cannot load the dialog for the environment variables any more, indicating that %windir% has been seriously hosed (compromised) across all applications. Bad bad bad....

Vista TaskDialog Wrapper: Unable to find an entry point named 'TaskDialogIndirect' in DLL 'ComCtl32'

I'm try to use Vista TaskDialog Wrapper and Emulator and I'm getting the following exception:
"Unable to find an entry point named 'TaskDialogIndirect' in DLL 'ComCtl32'."
...in a simple Console application:
class Program
{
[STAThread]
static void Main(string[] args)
{
System.Threading.Thread.CurrentThread.CurrentUICulture = System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");
PSTaskDialog.cTaskDialog.MessageBox(
"MessageBox Title",
"The main instruction text for the message box is shown here.",
"The content text for the message box is shown here and the text willautomatically wrap as needed.",
PSTaskDialog.eTaskDialogButtons.YesNo,
PSTaskDialog.eSysIcons.Information
);
}
}
What am I doing wrong?
UPDATE:
Actually, I'm working on an Excel plugin using excel-dna. How can I control what dll Excel loads?
http://exceldna.codeplex.com/discussions/286990#post728888

I haven't been at Office programming in a while, but my guess is that Excel loads both versions of comctl32, so you may need to use the Activation Context API to direct your code to the version that includes TaskDialog. Some ideas for fixing the problem (not solutions as such):
For test purposes, make a temporary enumeration of all modules in the active process - just to check if 6.10 is actually loaded (see below for a simple example of such an enumeration, albeit with a different intent).
Use the Activation Context API to get to the right version. Example of use from C# (for enabling themes by way of comctl32 6.0) here.
Alternatively (I never actually got this to work reliably in a WPF application I worked on), make a dialog abstraction class, which falls back to MessageDlg depending on the version available to you. There may be better ways of doing the check, but...:
FileVersionInfo version = ProcessUtils.GetLoadedModuleVersion("comctl32.dll");
if (version != null && version.FileMajorPart >= 6 && version.FileMinorPart >= 1)
{
// We can use TaskDialog...
}
else
{
// Use old style MessageBox
}
The enumeration of modules:
internal static FileVersionInfo GetLoadedModuleVersion(string name)
{
Process process = Process.GetCurrentProcess();
foreach (ProcessModule module in process.Modules)
{
if (module.ModuleName.ToLower() == name)
{
return module.FileVersionInfo;
}
return null;
}
}

In addition to what all the others are saying: This error will disappear if you set the ForceEmulationMode on PSTaskDialog to true.