(C# UWP/WinRT) PC/SC Wait for Smart Card Status Change (Inserted, Removed from Reader, etc.)

See more SCard Examples

Demonstrates how to synchronously wait for a status change, such as for a smart card to be inserted into a reader, or removed from a reader.

Note: This functionality was introduced in Chilkat v9.5.0.87.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.SCard scard = new Chilkat.SCard();

// First establish a context to the PC/SC Resource Manager
bool success = scard.EstablishContext("user");
if (success == false) {
    Debug.WriteLine(scard.LastErrorText);
    return;
}

// First we'll examine the state of all connected readers to see which have smartcards already inserted..
// Get JSON containing information about the smartcards currently inserted into readers.
// This also includes information about USB security tokens.
Chilkat.JsonObject json = new Chilkat.JsonObject();
success = scard.FindSmartcards(json);
if (success == false) {
    Debug.WriteLine(scard.LastErrorText);
    return;
}

// When writing this example, I have 3 smart card readers plugged into my system.
// One of them has a smart card inserted.
// Here's the JSON returned by FindSmartcards...

// {
//   "reader": [
//     {
//       "name": "Alcor Micro USB Smart Card Reader 0",
//       "state": "empty"
//     },
//     {
//       "name": "Generic Smart Card Reader Interface 0",
//       "state": "present",
//       "vendorName": "Generic",
//       "serialNumber": "3230303730383138303030303030303030",
//       "systemName": "Generic Smart Card Reader Interface 0",
//       "card": {
//         "atr": "3BFC180000813180459067464A00641606F2727E00E0",
//         "windows": {
//           "miniDriver": "tagliov70px.dll",
//           "cryptoProvider": "Microsoft Base Smart Card Crypto Provider",
//           "keyStorageProvider": "Microsoft Smart Card Key Storage Provider"
//         }
//       }
//     },
//     {
//       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
//       "state": "empty"
//     }
//   ]
// }

json.EmitCompact = false;
Debug.WriteLine(json.Emit());
Debug.WriteLine(" ");

// We can iterate over the JSON to find the readers with a smart card already inserted..
string name;
Chilkat.StringBuilder sbState = new Chilkat.StringBuilder();

int i = 0;
int count_i = json.SizeOfArray("reader");
while (i < count_i) {
    json.I = i;
    name = json.StringOf("reader[i].name");

    sbState.Clear();
    json.StringOfSb("reader[i].state",sbState);

    if (sbState.Contains("present",true) == true) {
        Debug.WriteLine(name + " has a smart card inserted.");
    }
    else {
        Debug.WriteLine(name + " does not have a smart card inserted.");
    }

    i = i + 1;
}

Debug.WriteLine(" ");

// Now let's begin the code to wait for a change (where a smart card gets inserted or removed)

// Get the list of all readers.
Chilkat.StringTable stReaders = new Chilkat.StringTable();
success = scard.ListReaders(stReaders);
if (success == false) {
    Debug.WriteLine(scard.LastErrorText);
    return;
}

// Show the reader names..
int numReaders = stReaders.Count;
i = 0;
while (i < numReaders) {
    Debug.WriteLine(Convert.ToString(i) + ": " + stReaders.StringAt(i));
    i = i + 1;
}

// Sample output from the above loop.
// 0: Alcor Micro USB Smart Card Reader 0
// 1: Generic Smart Card Reader Interface 0
// 2: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
// 

// Synchronously wait 30 seconds for a card to be inserted or removed from any of the above readers.
Chilkat.JsonObject json2 = new Chilkat.JsonObject();
success = await scard.GetStatusChangeAsync(30000,stReaders,json2);
if (success == false) {
    Debug.WriteLine(scard.LastErrorText);
    return;
}

Debug.WriteLine(" ");

// Let's see what happened...
json2.EmitCompact = false;
Debug.WriteLine(json2.Emit());
Debug.WriteLine(" ");

// This is what json2 contains.
// A card was inserted into the reader named "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
// The "numChanged" indicates that one reader's status changed.  
// The "changed":true indicates the reader that changed.   The state is now "present".

// {
//   "numChanged": 1,
//   "reader": [
//     {
//       "name": "Alcor Micro USB Smart Card Reader 0",
//       "changed": false,
//       "state": "empty"
//     },
//     {
//       "name": "Generic Smart Card Reader Interface 0",
//       "changed": false,
//       "state": "present",
//       "atr": "3BFC180000813180459067464A00641606F2727E00E0"
//     },
//     {
//       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
//       "changed": true,
//       "state": "present",
//       "atr": "3BDF96FF8131FE455A018048494443313158587300011B09"
//     }
//   ]
// }

// Find the reader that changed...
bool changed;
string state;
string atr;

int numChanged = json2.IntOf("numChanged");
Debug.WriteLine("number of readers with a changed state: " + Convert.ToString(numChanged));

i = 0;
count_i = json2.SizeOfArray("reader");
while (i < count_i) {
    json2.I = i;
    changed = json2.BoolOf("reader[i].changed");
    if (changed == true) {
        name = json2.StringOf("reader[i].name");
        state = json2.StringOf("reader[i].state");

        Debug.WriteLine("Changed: ");
        Debug.WriteLine("    reader name: " + name);
        Debug.WriteLine("    new state: " + state);

        // If a card is now in this reader, we should have the ATR of the card..
        if (json2.HasMember("reader[i].atr") == true) {
            atr = json2.StringOf("reader[i].atr");
            Debug.WriteLine("    ATR of card inserted into this reader: " + atr);
        }

    }

    i = i + 1;
}

// The output from the above loop:

// number of readers with a changed state: 1
// Changed: 
//     reader name: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
//     new state: present
//     ATR of card inserted into this reader: 3BDF96FF8131FE455A018048494443313158587300011B09

// Applications should always release the context when finished.
success = scard.ReleaseContext();
if (success == false) {
    Debug.WriteLine(scard.LastErrorText);
}