C# Comparing an Input to a String Exactly

Question

I have a list of most of the elements in the periodic table in order of their placement on the table:

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Chemistry_Element_Calculator
{
    class Program
    {
        static void Main(string[] args)
        {
            // Declare all numbers
            int electronNumber;
            int protonNumber;
            float neutronNumber;
            int i;

            // Declare all strings
            string elementRequest;

            // Create an list for all elements
            List<string> elementNameList = new List<string>();
            List<string> elementSymbolList = new List<string>();

            // Add all elements to the list
            elementNameList.Add("Hydrogen"); elementSymbolList.Add("H");
            elementNameList.Add("Helium"); elementSymbolList.Add("He");
            elementNameList.Add("Lithium"); elementSymbolList.Add("Li");
            elementNameList.Add("Beryllium"); elementSymbolList.Add("Be");
            elementNameList.Add("Boron"); elementSymbolList.Add("B");
            elementNameList.Add("Carbon"); elementSymbolList.Add("C");
            elementNameList.Add("Nitrogen"); elementSymbolList.Add("N");
            elementNameList.Add("Oxygen"); elementSymbolList.Add("O");
            elementNameList.Add("Fluorine"); elementSymbolList.Add("F");
            elementNameList.Add("Neon"); elementSymbolList.Add("Ne");
            elementNameList.Add("Sodium"); elementSymbolList.Add("Na");
            elementNameList.Add("Magnesium"); elementSymbolList.Add("Mg");
            elementNameList.Add("Aluminium"); elementSymbolList.Add("Al");
            elementNameList.Add("Silicon"); elementSymbolList.Add("Si");
            elementNameList.Add("Phosphorus"); elementSymbolList.Add("P");
            elementNameList.Add("Sulfur"); elementSymbolList.Add("S");
            elementNameList.Add("Chlorine"); elementSymbolList.Add("Cl");
            elementNameList.Add("Argon"); elementSymbolList.Add("Ar");
            elementNameList.Add("Potassium"); elementSymbolList.Add("K");
            elementNameList.Add("Calcium"); elementSymbolList.Add("Ca");
            elementNameList.Add("Scandium"); elementSymbolList.Add("Sc");
            elementNameList.Add("Titanium"); elementSymbolList.Add("Ti");
            elementNameList.Add("Vanadium"); elementSymbolList.Add("V");
            elementNameList.Add("Chromium"); elementSymbolList.Add("Cr");
            elementNameList.Add("Manganese"); elementSymbolList.Add("Mn");
            elementNameList.Add("Iron"); elementSymbolList.Add("Fe");
            elementNameList.Add("Cobalt"); elementSymbolList.Add("Co");
            elementNameList.Add("Nickel"); elementSymbolList.Add("Ni");
            elementNameList.Add("Copper"); elementSymbolList.Add("Cu");
            elementNameList.Add("Zinc"); elementSymbolList.Add("Zn");
            elementNameList.Add("Gallium"); elementSymbolList.Add("Ga");
            elementNameList.Add("Germanium"); elementSymbolList.Add("Ge");
            elementNameList.Add("Arsenic"); elementSymbolList.Add("As");
            elementNameList.Add("Selenium"); elementSymbolList.Add("Se");
            elementNameList.Add("Bromine"); elementSymbolList.Add("Br");
            elementNameList.Add("Krypton"); elementSymbolList.Add("Kr");
            elementNameList.Add("Rubidium"); elementSymbolList.Add("Rb");
            elementNameList.Add("Strontium"); elementSymbolList.Add("Sr");
            elementNameList.Add("Yttrium"); elementSymbolList.Add("Y");
            elementNameList.Add("Zirconium"); elementSymbolList.Add("Zr");
            elementNameList.Add("Niobium"); elementSymbolList.Add("Nb");
            elementNameList.Add("Molybdenum"); elementSymbolList.Add("Mo");
            elementNameList.Add("Technetium"); elementSymbolList.Add("Tc");
            elementNameList.Add("Rubidium"); elementSymbolList.Add("Ru");
            elementNameList.Add("Rhodium"); elementSymbolList.Add("Rh");
            elementNameList.Add("Palladium"); elementSymbolList.Add("Pd");
            elementNameList.Add("Silver"); elementSymbolList.Add("Ag");
            elementNameList.Add("Cadmium"); elementSymbolList.Add("Cd");
            elementNameList.Add("Indium"); elementSymbolList.Add("In");
            elementNameList.Add("Tin"); elementSymbolList.Add("Sn");
            elementNameList.Add("Antimony"); elementSymbolList.Add("Sb");
            elementNameList.Add("Tellurium"); elementSymbolList.Add("Te");
            elementNameList.Add("Iodine"); elementSymbolList.Add("I");
            elementNameList.Add("Xenon"); elementSymbolList.Add("Xe");
            elementNameList.Add("Caesium"); elementSymbolList.Add("Cs");
            elementNameList.Add("Barium"); elementSymbolList.Add("Ba");
            elementNameList.Add("Lanthanum"); elementSymbolList.Add("La");
            elementNameList.Add("Cerium"); elementSymbolList.Add("Ce");
            elementNameList.Add("Praseodynium"); elementSymbolList.Add("Pr");
            elementNameList.Add("Neodymium"); elementSymbolList.Add("Nd");
            elementNameList.Add("Promethium"); elementSymbolList.Add("Pm");
            elementNameList.Add("Samarium"); elementSymbolList.Add("Sm");
            elementNameList.Add("Europium"); elementSymbolList.Add("Eu");
            elementNameList.Add("Gadolinium"); elementSymbolList.Add("Gd");
            elementNameList.Add("Terbium"); elementSymbolList.Add("Tb");
            elementNameList.Add("Dysprosium"); elementSymbolList.Add("Dy");
            elementNameList.Add("Holomium"); elementSymbolList.Add("Ho");
            elementNameList.Add("Erbium"); elementSymbolList.Add("Er");
            elementNameList.Add("Thulium"); elementSymbolList.Add("Tm");
            elementNameList.Add("Ytterbium"); elementSymbolList.Add("Yb");
            elementNameList.Add("Lutenium"); elementSymbolList.Add("Lu");
            elementNameList.Add("Hafnium"); elementSymbolList.Add("Hf");
            elementNameList.Add("Tantalum"); elementSymbolList.Add("Ta");
            elementNameList.Add("Tungsten"); elementSymbolList.Add("W");
            elementNameList.Add("Rhenium"); elementSymbolList.Add("Re");
            elementNameList.Add("Osmium"); elementSymbolList.Add("Os");
            elementNameList.Add("Iridium"); elementSymbolList.Add("Ir");
            elementNameList.Add("Platinum"); elementSymbolList.Add("Pt");
            elementNameList.Add("Gold"); elementSymbolList.Add("Au");
            elementNameList.Add("Mercury"); elementSymbolList.Add("Hg");
            elementNameList.Add("Thallium"); elementSymbolList.Add("Tl");
            elementNameList.Add("Lead"); elementSymbolList.Add("Pb");
            elementNameList.Add("Bismuth"); elementSymbolList.Add("Bi");
            elementNameList.Add("Polonium"); elementSymbolList.Add("Po");
            elementNameList.Add("Astatine"); elementSymbolList.Add("At");
            elementNameList.Add("Radon"); elementSymbolList.Add("Rn");
            elementNameList.Add("Francium"); elementSymbolList.Add("Fr");
            elementNameList.Add("Radium"); elementSymbolList.Add("Ra");
            elementNameList.Add("Actinium"); elementSymbolList.Add("Ac");
            elementNameList.Add("Thorium"); elementSymbolList.Add("Th");
            elementNameList.Add("Palladium"); elementSymbolList.Add("Pa");
            elementNameList.Add("Uranium"); elementSymbolList.Add("U");
            elementNameList.Add("Nepturium"); elementSymbolList.Add("Np");
            elementNameList.Add("Plutonium"); elementSymbolList.Add("Pu");
            elementNameList.Add("Americium"); elementSymbolList.Add("Am");
            elementNameList.Add("Curium"); elementSymbolList.Add("Cm");
            elementNameList.Add("Berkelium"); elementSymbolList.Add("Bk");
            elementNameList.Add("Californium"); elementSymbolList.Add("Cf");
            elementNameList.Add("Einsteinium"); elementSymbolList.Add("Es");
            elementNameList.Add("Fermium"); elementSymbolList.Add("Fermium");
            elementNameList.Add("Mendelevium"); elementSymbolList.Add("Md");
            elementNameList.Add("Nobelium"); elementSymbolList.Add("No");
            elementNameList.Add("Lawrencium"); elementSymbolList.Add("Lr");
            elementNameList.Add("Rutherfordium"); elementSymbolList.Add("Rf");
            elementNameList.Add("Dubnium"); elementSymbolList.Add("Db");
            elementNameList.Add("Seaborgium"); elementSymbolList.Add("Sg");
            elementNameList.Add("Bohrium"); elementSymbolList.Add("Bh");
            elementNameList.Add("Hassium"); elementSymbolList.Add("Hs");
            elementNameList.Add("Meitnerium"); elementSymbolList.Add("Mt");
            elementNameList.Add("Darmstadtium"); elementSymbolList.Add("Ds");
            elementNameList.Add("Roentgenium"); elementSymbolList.Add("Rg");
            elementNameList.Add("Copernicium"); elementSymbolList.Add("Cn");

            Console.WriteLine("What element do you want? Either input it's full name, with a capital letter, or it's elemnent symbol. E.g. N for Nitrogen");
            elementRequest = Console.ReadLine();


            elementNameList.ForEach(delegate (String elementName)
                {
                    if (elementRequest == elementName)
                    {
                        Console.WriteLine("Hydrogen");
                    }
                    else
                    {
                        Console.WriteLine("Not Hydrogen");
                    };
                });
            Console.Read();

However, when I run the program, and input Hydrogen, both Helium and Hydrogen are said to be hydrogen. How can I fix this?

Also, if anyone has an idea on how to compress the 2 lists so they're smaller, let me know :)

Thanks :)

`Console.writeline("Hydrogen")` will always say it's hydrogen if it finds the requested element. Write `Console.writeline(elementName & " has been found in the list")` — Martin Verjans, Sep 29 '16 at 09:45
It's because "elementRequest == elementName" is true for the input "Helium" when tested against the "Helium" element in the list. — Owen Pauling, Sep 29 '16 at 09:46
you don't have to use for each, just use `if(elementNameList.Contains(elementRequest ))` — Haitham Shaddad, Sep 29 '16 at 09:46
You can create class `Element` that has two properties `Name` and `Symbol` and then create a list `List` — ElectricRouge, Sep 29 '16 at 09:46

CodeCaster · Accepted Answer · 2016-09-29T10:55:39.450

3

What you want your code to do is take the index from the first list, and return the string at the same index in the second list.

Your code is currently not doing any of that, but always printing "Hydrogen", your output thus always being "Hydrogen" whatever element is requested.

You can trivially fix that by actually looking up the index:

int indexOfElementName = elementNameList.IndexOf(elementRequest);
string elementSymbol = elementSymbolList[indexOfElementName];

Note that that does not handle casing and requested elements that aren't in the list (or typos).

But keeping the two lists in sync, and this code in general, is a maintenance disaster waiting to happen.

Instead you could use a dictionary where the element name is the key and the symbol the value:

var elementDictionary = new Dictionary<string, string>
{
    { "Hydrogen", "H" },
    { "Helium", "He" },
    // ...
}

Then look it up:

string elementSymbol = elementDictionary[elementRequest];

Do note that this still doesn't handle case-insensitivity and elements that are not found, but I'll leave that as an exercise to you.

edited Sep 29 '16 at 10:55

answered Sep 29 '16 at 09:46

CodeCaster

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which is faster dictionary or hash table? – Anonymous Duck Sep 29 '16 at 09:50
1

My answer to _"which is faster"_ is generally _"you shouldn't care until it proves to be a problem"_. – CodeCaster Sep 29 '16 at 09:50
nice answer. given if there are same big volume of data stored in the ff data structures – Anonymous Duck Sep 29 '16 at 09:52
I'll try this now. Thanks! :D – Bob Sep 29 '16 at 09:53
@Sherlock read [HashSet versus Dictionary w.r.t searching time to find if an item exists](http://stackoverflow.com/questions/2728500/hashsett-versus-dictionaryk-v-w-r-t-searching-time-to-find-if-an-item-exist) and [Which is faster?](https://ericlippert.com/2012/12/17/performance-rant/). – CodeCaster Sep 29 '16 at 09:54
I read that there is no difference since both of them maintain a hash table internally :3 – Anonymous Duck Sep 29 '16 at 09:54
@CodeCaster the line var elementSymbol= element.Value; gives the error 'string' does not contain a definition for 'Value' and no extension method 'Value' accepting a first argument of type 'string' could be found (are you missing a using directive or an assembly reference?) – Bob Sep 29 '16 at 10:53
@Bob of course, the result of a dictionary lookup is already the value, see edit. – CodeCaster Sep 29 '16 at 10:55
@CodeCaster Thanks for the help! :D – Bob Sep 29 '16 at 11:01

score 3 · Answer 2 · edited May 23 '17 at 12:33

I would use a custom class and a list as suggested by ElectricRouge.

I don't favor the dictionary because you need to search both by name and symbol. Also, the data set is small (118 elements to date).

See comments for the explanation of the code.

using System;
using System.Collections.Generic;

namespace Chemistry_Element_Calculator
{
    // Create a chemical element class
    // You can add more properties such as number of electrons, etc.
    public class ChemicalElement
    {
        public string Symbol
        {
            get; set;
        }

        public string Name
        {
            get; set;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            // Create a list of the elements, populate their properties
            var elements = new List<ChemicalElement>()
            {
                new ChemicalElement {Name = "Hydrogen", Symbol = "H"},
                new ChemicalElement {Name = "Helium", Symbol = "He"},
                new ChemicalElement {Name = "Lithium", Symbol = "Li"}
                // etc.
            };

            Console.WriteLine("What element do you want? Either input it's full name, with a capital letter, or it's elemnent symbol. E.g. N for Nitrogen");
            var elementRequest = Console.ReadLine();

            // Use find to get a matching element, compare both name and symbol
            var foundElement = elements.Find(element => element.Symbol == elementRequest || element.Name == elementRequest);

            if (foundElement == null)
            {
                // Output if no element is found
                Console.WriteLine("Element Not Found");
            }
            else
            {
                // Output if the element is found
                Console.WriteLine("Found element {0}.", foundElement.Name);
            }

            Console.WriteLine("[Press any key to finish]");
            Console.ReadKey();
        }
    }
}

The code uses the method List.Find to get the result, it will only return the first match.

I would also suggest to migrate to String.Compare if you want to have case-insensitive comparison.

And finally I would be reading the data form file or a database, but that is beyond the question.

C# Comparing an Input to a String Exactly

2 Answers2