Develop Reference

Get current state of webcam in C#

I am trying to figure out how to check if a webcam/video capture device is already being used by another application without actually activating it.
My current approach is to use the AForge.NET library and using the .IsRunning property of the VideoCaptureDevice object like this:
var videoDevices = new FilterInfoCollection(FilterCategory.VideoInputDevice);
foreach (FilterInfo videoDevice in videoDevices)
{
VideoCaptureDevice camera new AForge.Video.DirectShow.VideoCaptureDevice(videoDevice.MonikerString);
Debug.Print(camera.IsRunning)
}
I guess the IsRunning property only works on VideoCaptureDevices that have been started using the library and I need lower-level DirectShow access to the device.
While there are many ways to use DirectShow in C#, I have been unable to find a way to check the state even using DirectShow in C++. Is there some magic I need to perform here?
Thanks
Tobias Timpe

I'm not entirely sure if this will be helpful to you, but I found your question because I wanted to write a custom app to control my busylight. This is very much 'Works On My Machine' certified - it's not an attempt to give a general answer. However, I figure it may help you, and possibly the next person who comes across this page while googling...
private static bool IsWebCamInUse()
{
using (var key = Registry.CurrentUser.OpenSubKey(#"SOFTWARE\Microsoft\Windows\CurrentVersion\CapabilityAccessManager\ConsentStore\webcam\NonPackaged"))
{
foreach (var subKeyName in key.GetSubKeyNames())
{
using (var subKey = key.OpenSubKey(subKeyName))
{
if (subKey.GetValueNames().Contains("LastUsedTimeStop"))
{
var endTime = subKey.GetValue("LastUsedTimeStop") is long ? (long) subKey.GetValue("LastUsedTimeStop") : -1;
if (endTime <= 0)
{
return true;
}
}
}
}
}
return false;
}

Controlling Application's Volume & VU Meter

I am using NAudio for a screen recording software I am designing and I need to know if it's possible to not only control the specific application's volume but also display a VU Meter for the application's sound.
I've Googled all over the place and it seems I can only get a VU Meter for the devices currently on my computer and set the volume for those devices.
Even though I am using NAudio, I am open to other solutions.

I asked the question in more detail after this question. I have since found the answer so I will leave the answer here for those who stumble upon it. Trying to use NAudio & CSCore has gotten me quite familiar with so please ask if you need further assistance.
This block of code uses CSCore and is a modified and commented version of the answer found here:Getting individual windows application current volume output level as visualized in audio Mixer
class PeakClass
{
static int CurrentProcessID = 0000;
private static void Main(string[] args)
{
//Basically gets your default audio device and session attached to it
using (var sessionManager = GetDefaultAudioSessionManager2(DataFlow.Render))
{
using (var sessionEnumerator = sessionManager.GetSessionEnumerator())
{
//This will go through a list of all processes uses the device
//the code got two line above.
foreach (var session in sessionEnumerator)
{
//This block of code will get the peak value(value needed for VU Meter)
//For whatever process you need it for (I believe you can also check by name
//but I found that less reliable)
using (var session2 = session.QueryInterface<AudioSessionControl2>())
{
if(session2.ProcessID == CurrentProcessID)
{
using (var audioMeterInformation = session.QueryInterface<AudioMeterInformation>())
{
Console.WriteLine(audioMeterInformation.GetPeakValue());
}
}
}
//Uncomment this block of code if you need the peak values
//of all the processes
//
//using (var audioMeterInformation = session.QueryInterface<AudioMeterInformation>())
//{
// Console.WriteLine(audioMeterInformation.GetPeakValue());
//}
}
}
}
}
private static AudioSessionManager2 GetDefaultAudioSessionManager2(DataFlow dataFlow)
{
using (var enumerator = new MMDeviceEnumerator())
{
using (var device = enumerator.GetDefaultAudioEndpoint(dataFlow, Role.Multimedia))
{
Console.WriteLine("DefaultDevice: " + device.FriendlyName);
var sessionManager = AudioSessionManager2.FromMMDevice(device);
return sessionManager;
}
}
}
}
The following code block will allow you to change the volume of the device using NAudio
MMDevice VUDevice;
public void SetVolume(float vol)
{
if(vol > 0)
{
VUDevice.AudioEndpointVolume.Mute = false;
VUDevice.AudioEndpointVolume.MasterVolumeLevelScalar = vol;
}
else
{
VUDevice.AudioEndpointVolume.Mute = true;
}
Console.WriteLine(vol);
}
I have code from two different libraries only to answer the question I posted directly which was how to both set the volume and get VU Meter values (peak values). CSCore and NAudio are very similar so most of the code here is interchangeable.

Smart Card Reader, can't read some cards

I have an application that is using an smart card reader for allowing the users to access parts of the system. On one location i have no issues. But another, which have an different type of card manufacturer has a lot of issues. It keeps getting an id of zero back. Then looking into the eventlog i saw this:
And this is the code:
card.Connect(reader, SHARE.Shared, PROTOCOL.T0orT1);
var apduGetID = new APDUCommand(0xFF, 0xCA, 0, 0, null, 4);
var apduRespGetID = card.Transmit(apduGetID);
long cardId = BitConverter.ToUInt32(apduRespGetID.Data.Reverse().ToArray(), 0);
the second problem is that then trying to debug the code, it works perfect, only then remove the breakpoint can i see the issue but not where. Can some one please help me?
P.S. i found this thread, but it does not work: https://superuser.com/questions/715688/smart-card-errors
Update: Here are the Transmit class
public override APDUResponse Transmit(APDUCommand ApduCmd)
{
var RecvLength = (uint)(ApduCmd.Le + APDUResponse.SW_LENGTH);
byte[] ApduBuffer;
var ApduResponse = new byte[ApduCmd.Le + APDUResponse.SW_LENGTH];
var ioRequest = new SCard_IO_Request
{
m_dwProtocol = m_nProtocol,
m_cbPciLength = 8
};
// Build the command APDU
if (ApduCmd.Data == null)
{
ApduBuffer = new byte[APDUCommand.APDU_MIN_LENGTH + ((ApduCmd.Le != 0) ? 1 : 0)];
if (ApduCmd.Le != 0)
{
ApduBuffer[4] = ApduCmd.Le;
}
}
else
{
ApduBuffer = new byte[APDUCommand.APDU_MIN_LENGTH + 1 + ApduCmd.Data.Length];
for (var nI = 0; nI < ApduCmd.Data.Length; nI++)
{
ApduBuffer[APDUCommand.APDU_MIN_LENGTH + 1 + nI] = ApduCmd.Data[nI];
}
ApduBuffer[APDUCommand.APDU_MIN_LENGTH] = (byte)ApduCmd.Data.Length;
}
ApduBuffer[0] = ApduCmd.Class;
ApduBuffer[1] = ApduCmd.Ins;
ApduBuffer[2] = ApduCmd.P1;
ApduBuffer[3] = ApduCmd.P2;
m_nLastError = SCardTransmit(m_hCard, ref ioRequest, ApduBuffer, (uint)ApduBuffer.Length, IntPtr.Zero, ApduResponse, out RecvLength);
if (m_nLastError != 0)
{
var msg = "SCardTransmit error: " + m_nLastError;
throw new SmartCardException(msg, m_nLastError);
}
var apduData = new byte[RecvLength];
for (var nI = 0; nI < RecvLength; nI++)
{
apduData[nI] = ApduResponse[nI];
}
return new APDUResponse(apduData);
}
Update 2: I have also tried with to put some Thread.Sleep()

Please check that on the second machine you have all the up-to-date drivers of the smart card. Also, sometimes it helps to replace the driver which is provided by the manufacturer with "Microsoft WUDF driver" - https://msdn.microsoft.com/en-us/library/windows/hardware/dn653571(v=vs.85).aspx
Please note, that you have two type of devices detected by the OS when you plug it in - the smart card enumerator device (smart card reader) and the smart card (sometimes called the smart card container) itself. One smart card reader can contain several smart cards.
Example of the smart card which driver was forcefully replaced with Microsoft WUDF to make the client application (iBank2) work:
The four smart card drivers have been forcefully replaced with basic Microsoft driver to make the application work.

Well if the other system does not take your smart card,just check the BIOS settings for smartcard.There is an option to disable/enable them in some systems.

Cosmos custom OS, addmapping?

I am new to C# and is currently using COSMOS to make a simple FileSystem for my OS class. Currently I'm trying to implement a "reformat" function that, when the word "reformat" is typed into the console, the OS (emulated via QEMU), partitions the disk. Currently this is my code:
public static void console()
{
while (true)
{
Console.WriteLine("Console: ");
String input = Console.ReadLine();
if (input == "exit")
{
Cosmos.Sys.Deboot.ShutDown();
}
else if (input == "cpumem")
{
Console.WriteLine(Cosmos.Kernel.CPU.AmountOfMemory.ToString());
}
else if (input == "restart")
{
Cosmos.Sys.Deboot.Reboot();
}
else if (input == "devices")
{
var devices = Cosmos.Sys.FileSystem.Disk.Devices.ToArray();
}
else if (input == "reformat")
{
try
{
Partition part = null;
for (int j = 0; j < Cosmos.Hardware.BlockDevice.Devices.Count; j++)
{
if (Cosmos.Hardware.BlockDevice.Devices[j] is Partition)
{
part = (Partition)Cosmos.Hardware.BlockDevice.Devices[j];
}
}
var fs = new Cosmos.Sys.FileSystem.FAT32.FAT32(part);
uint cluster = 100;
fs.Format("newCluster", cluster);
}
catch
{
//Do Something warn user.
}
}
}
}
Most important is this bit:
else if (input == "reformat")
{
try
{
Partition part = null;
for (int j = 0; j < Cosmos.Hardware.BlockDevice.Devices.Count; j++)
{
if (Cosmos.Hardware.BlockDevice.Devices[j] is Partition)
{
part = (Partition)Cosmos.Hardware.BlockDevice.Devices[j];
}
}
var fs = new Cosmos.Sys.FileSystem.FAT32.FAT32(part);
uint cluster = 100;
fs.Format("newCluster", cluster);
}
catch
{
//Do Something warn user.
}
}
Which is analogous to what is located here: http://cosmos-tutorials.webs.com/atafat.html
However, when I run it, I get this error:
I believe this is because I lack this line:
Cosmos.System.Filesystem.FileSystem.AddMapping("C", FATFS);
FATFileList = FATFS.GetRoot();
Located in the link above. Is there any other way to map? Or am I missing something completely? The COSMOS documentation doesn't really tell much, the source code is honestly confusing for a beginner like me as it has no comments whatsoever on how the functions work or what they do. I am using an older version of COSMOS (Milestone 4) as it's the only one that works for Visual Studio C# 2008. Newer versions run only in Visual Studio C# 2010.

Ah, I recognize this... had to debug a similar situation on a Cosmos project I'm working on myself (I'm using the VS2010-compatible Cosmos but the same situation might apply to older versions as well...)
This can happen if you try to call a method on a null object. Type 0x........, Method 0x........ is specifically mentioning the location in the compiled code where the call failed. "Not FOUND!" means that the method it is looking for cannot be found, presumably because you called it on a null reference.
I'm testing with VirtualBox myself, and found that if you're using a brand-new blank hard disk image, there will be no Partitions on it. Thus, the condition will never get satisfied, your Partition will never get set and then Cosmos will try to execute a method on the null Partition!
Look closely at how you set the Partition (it's initialized to null). For starters I would print a simple message each time the "if (block device is partition)" condition is satisfied... I would be willing to bet it will never print.
Hope this helps... I am still learning about Cosmos and custom kernels myself but fixing the null reference in my case solved my occurrence of the problem. If that's the problem, then the next step, of course, is figuring out why you're not getting any Partitions in the first place...
The rest of your code looks fine but I am not sure how you implemented the rest of your classes. Kernel debugging can be a nightmare, good luck to you!

Is there a way to check if a printing process was successful?

I have an application where I need to print a ticket. Each ticket must be unique. The application is windows forms and written entirely in c#. For our application we're using Samsung ML- 2525 laser monochromatic printers.
The flow is basically the following, the operator picks a product/ticket (which is unique) and then it presses a button that does 2 things:
Connects to a database and updates the product as used
Prints the ticket (this is done using System.Drawing and GDI+)
For some reason, every once in a while, the image that needs to be printed is not sent to the printer. It's a rare case, but it happens.
I tried to connect to the printer using Win32_Printer ( http://msdn.microsoft.com/en-us/library/Aa394363 ) but I can't get to get the current printer's state (online, offline, low toner, paper jam, etc). I can only check if the printer exists and that the paper size is installed correctly. I tried code similar to the following but it didn't work
private string MonitorPrintJobWmi()
{
var jobMessage = String.Empty;
var scope = new ManagementScope(ManagementPath.DefaultPath);
scope.Connect();
var selectQuery = new SelectQuery { QueryString = #"select * from Win32_PrintJob" };
var objSearcher = new ManagementObjectSearcher(scope, selectQuery);
var objCollection = objSearcher.Get();
foreach (var job in objCollection)
{
if (job != null)
{
jobMessage += String.Format("{0} \r\n", job["Name"].ToString());
jobMessage += String.Format("{0} \r\n", job["JobId"].ToString());
_jobId = Convert.ToInt32(job["JobId"]);
jobMessage += String.Format("{0} \r\n", job["JobStatus"].ToString());
jobMessage += String.Format("{0} \r\n", job["Status"].ToString());
}
}
return jobMessage;
}
I tried to get an API for the printer but I couldn't get a hold of it. By the way, the printer's software do indicate different errors in the windows toolbar.
My question is if anyone can lead me in the right direction as to how to connect to a printer and check if printing was successful.
Also, it would be helpful if someone know of some other specific printer in which I may accomplish this ie, changing hardware.
Thanks,

To get a list of print queues on the local machine, try PrintServer's GetPrintQueues method.
Once you have an instance of the PrintQueue object associated with the relevant printer, you can use it to access the printer's status (IsOffline, IsPaperOut, etc.). Also, you can use it to get a list of the jobs in the given queue (GetPrintJobInfoCollection) which then will allow you to get job-specific status information (IsInError, IsCompleted, IsBlocked, etc.).
Hope this helps!

After try to print your PrintDocument (System.Drawing.Printing), try to check status of printjobs.
First step: Initialize your printDocument.
Second step: Get your printer Name From System.Drawing.Printing.PrinterSettings.InstalledPrinters.Cast<string>();
And copy it into your printerDocument.PrinterSettings.PrinterName
Third step: Try to print and dispose.
printerDocument.Print();
printerDocument.Dispose();
Last step: Run the check in a Task (do NOT block UI thread).
Task.Run(()=>{
if (!IsPrinterOk(printerDocument.PrinterSettings.PrinterName,checkTimeInMillisec))
{
// failed printing, do something...
}
});
Here is the implementation:
private bool IsPrinterOk(string name,int checkTimeInMillisec)
{
System.Collections.IList value = null;
do
{
//checkTimeInMillisec should be between 2000 and 5000
System.Threading.Thread.Sleep(checkTimeInMillisec);
// or use Timer with Threading.Monitor instead of thread sleep
using (System.Management.ManagementObjectSearcher searcher = new System.Management.ManagementObjectSearcher("SELECT * FROM Win32_PrintJob WHERE Name like '%" + name + "%'"))
{
value = null;
if (searcher.Get().Count == 0) // Number of pending document.
return true; // return because we haven't got any pending document.
else
{
foreach (System.Management.ManagementObject printer in searcher.Get())
{
value = printer.Properties.Cast<System.Management.PropertyData>().Where(p => p.Name.Equals("Status")).Select(p => p.Value).ToList();
break;
}
}
}
}
while (value.Contains("Printing") || value.Contains("UNKNOWN") || value.Contains("OK"));
return value.Contains("Error") ? false : true;
}
Good luck.