Dictionary Key look up with variable length inputs

Question

I am decoding GS1 barcodes and need to match up application identifiers with relevant data about them.

00 SSCC (Serial Shipping Container Code) N2+N18 FALSE SSCC 
01 Global Trade Item Number (GTIN) N2+N14 FALSE GTIN 
02 GTIN of Contained Trade Items N2+N14 FALSE CONTENT 
10 Batch or Lot Number N2+X.20 TRUE BATCH/LOT 
11 Production Date (YYMMDD) N2+N6 FALSE PROD DATE 
12 Due Date (YYMMDD) N2+N6 FALSE DUE DATE 
13 Packaging Date (YYMMDD) N2+N6 FALSE PACK DATE 
15 Best Before Date (YYMMDD) N2+N6 FALSE BEST BEFORE or BEST BY 
16 Sell By Date (YYMMDD) N2+N6 FALSE SELL BY 
17 Expiration Date (YYMMDD) N2+N6 FALSE USE BY OR EXPIRY 
20 Variant Number N2+N2 FALSE VARIANT 
21 Serial Number N2+X.20 TRUE SERIAL 
240 Additional Item Identification N3+X.30 TRUE ADDITIONAL ID 
241 Customer Part Number N3+X.30 TRUE CUST. PART NO. 
242 Made-to-Order Variation Number N3+N.6 TRUE MTO VARIANT 
243 Packaging Component Number N3+X.20 TRUE PCN 
250 Secondary Serial Number N3+X.30 TRUE SECONDARY SERIAL 
251 Reference to Source Entity N3+X.30 TRUE REF. TO SOURCE 
253 Global Document Type Identifier (GDTI) N3+N13+XTRUE GDTI 
254 GLN Extension Component N3+X.20 TRUE GLN EXTENSION COMPONENT 
255 Global Coupon Number (GCN) N3+N13+NTRUE GCN 
30 Count of Items (Variable Measu ... N2+N..8 TRUE VAR. COUNT 
3100 Net weight kilograms (Var... ) N4+N6 FALSE NET WEIGHT (kg) 
...

Full list here.

This is how I identify them:

public Dictionary<int, Tuple<string, string, bool, string>> gs1AiDict { get; private set; } 
var aiDataOut = new Tuple<string, string, bool, string>("","",false,"");
//Get first 4 digits (max identifier length)
//the string input pi might look like this: ~10000123
int applicationIdentifier = Convert.ToInt16(pi.Substring(1,4));
//Try to find an identifier with 2 digits.
if (gs1AiDict.TryGetValue(applicationIdentifier / 100, out aiDataOut))
{
 //assign found data to tuple
 id = aiDataOut.Item1;
 format = aiDataOut.Item2;
 func = aiDataOut.Item3;
 abrv = aiDataOut.Item4;
}
//look up the first 3 digits
else
{
 if (gs1AiDict.TryGetValue(applicationIdentifier / 10, out aiDataOut))
 {
 id = aiDataOut.Item1;
 format = aiDataOut.Item2;
 func = aiDataOut.Item3;
 abrv = aiDataOut.Item4;
 }
 //look up first 4 digits
 else
 {
 if (gs1AiDict.TryGetValue(applicationIdentifier, out aiDataOut))
 {
 id = aiDataOut.Item1;
 format = aiDataOut.Item2;
 func = aiDataOut.Item3;
 abrv = aiDataOut.Item4;
 }
 //no identifiers are 5 digits
 else
 {
 console.log("No Application Identifier found!");
 }
 }
}

My tests have worked wonderfully, but my issue is the readability and efficiency of this solution. Are 3 dictionary key look ups for about 140 keys too much?

Answer 1

Code duplication is a sin

You could use shorter and more readable code using a simple for loop:

int applicationIdentifier = Convert.ToInt16(pi.Substring(1,4));
for (int i = 100; i >= 1; i /= 10)
{
 int maybeId = applicationIdentifier / i;
 if (gs1AiDict.TryGetValue(maybeId, out aiDataOut))
 {
 id = aiDataOut.Item1;
 format = aiDataOut.Item2;
 func = aiDataOut.Item3;
 abrv = aiDataOut.Item4;
 return;
 }
} 
Console.WriteLine("No Application Identifier found!");

You should also consider making your data object something along the lines of a Dicitionary<int, ApplicationInfo>, that 4-member tuple doesn't help readibility. Then you could also return an ApplicationInfo object instead of copying the fields to local variables.

• user4067565: Indeed that function is much cleaner. Regarding the use of "Application Info" to hold the data: could you point me to a use of that? When I was researching how to get multiple parameters per key, all I found were Tuples.
• Rotem: @Phyre ApplicationInfo is a name I made up, it's not a existing type. I was suggesting that you should create a class that holds a single entry of application information.