Lesson 09: Introduction to Strings

The Nullity of a String

A Null String

A string is referred to as null if it doesn't (yet) have a(ny) character(s)s. This is usually the case when the string has just been created, or a string variable has just been declared. When you have just declared a variable, to indicate that it is null, assign the null keyword to it. The variable must be declared using the string data type, the String class, or the dynamic keyword. Here are example:

@{ 
    string firstName = null;
    dynamic lastName = null;
    String homeAddress = null;
}

If you decide to use the var keyword to declare the variable, you cannot assign null to it.

A Null or Empty String

A string is referred to as null if it has lost its characters. To let you find out whether a string is empty or null, the String class is equipped with a static method named IsNullOrEmpty. Its syntax is:

public static bool IsNullOrEmpty(string value)

Practical Learning: Using a Null String

In the Solution Explorer, under Views and under Customers, double-click BillPreparation.cshtml to access it

Change the code as follows:

@{
    ViewBag.Title = "Customer Invoice Preparation";
}

<h2 class="text-center">Gas Utility Company</h2>

<h3 class="text-center">Customer Bill Preparation</h3>

<div class="horizontal-line"></div>

@{
    double CCFTotal = 0;
    double amountDue = 0;
    double localTaxes = 0;
    double stateTaxes = 0;
    double totalTherms = 0;
    double over50Therms = 0;
    double first50Therms = 0;
    double deliveryTotal = 0;
    double meterReadingEnd = 0;
    double meterReadingStart = 0;
    int    invoiceNumber = 100001;
    string strErrorMessage = null;
    double environmentalCharges = 0;
    double transportationCharges = 0;
    double distributionAdjustment = 0;

    if (IsPost)
    {
        try
        {
            if (string.IsNullOrEmpty(Request["txtMeterReadingStart"].ToString()))
            {
                throw new FormatException("Meter Start Error");
            }

            meterReadingStart = double.Parse(Request["txtMeterReadingStart"]);

            if (string.IsNullOrEmpty(Request["txtMeterReadingEnd"].ToString()))
            {
                throw new FormatException("Meter End Error");
            }

            meterReadingEnd = double.Parse(Request["txtMeterReadingEnd"]);

            CCFTotal = meterReadingEnd - meterReadingStart;
            totalTherms = CCFTotal * 1.0367;
            distributionAdjustment = totalTherms * 0.13086;
            if (totalTherms <= 5000)
            {
                transportationCharges = totalTherms * 0.016289;
            }
            else
            {
                transportationCharges = totalTherms * 0.009577;
            }

            if (totalTherms < 5000)
            {
                first50Therms = totalTherms * 0.02269;
                over50Therms = 0;
            }
            else
            {
                first50Therms = 5000 * 0.02269;
                over50Therms = (totalTherms - 5000) * 0.04995;
            }

            deliveryTotal = transportationCharges + distributionAdjustment + first50Therms + over50Therms;
            environmentalCharges = deliveryTotal * 0.0045;

            localTaxes = (deliveryTotal + environmentalCharges) * 0.04862;
            stateTaxes = (deliveryTotal + environmentalCharges) * 0.020943;

            amountDue = deliveryTotal + environmentalCharges + localTaxes + stateTaxes;
        }
        catch (FormatException fe)
        {
            if (fe.Message == "Meter Start Error")
            {
                strErrorMessage = "Either you left the meter start text box empty or you entered an invalid value.";
            }

            if (fe.Message == "Meter End Error")
            {
                strErrorMessage = "The value provided for the counter end reading is not valid.";
            }
        }
    }
}

@using (Html.BeginForm())
{
    <table>
        <tr>
            <td class="left-column">Invoice #:</td>
            <td class="left-text-boxes">@Html.TextBox("txtInvoiceNumber", @invoiceNumber, new { @class = "txtContext" })</td>
            <td class="right-label">&nbsp;</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td>Counter Reading Start:</td>
            <td>@Html.TextBox("txtMeterReadingStart", @meterReadingStart, new { @class = "txtContext" })</td>
            <td>Counter Reading End:</td>
            <td>@Html.TextBox("txtMeterReadingEnd", @meterReadingEnd, new { @class = "txtContext" })</td>
        </tr>
    </table>
    <p class="text-center"><input type="submit" class="btnLarge" value="Prepare Invoice" name="btnPrepareInvoice" /></p>
    <div class="horizontal-line"></div>
    <table>
        <tr>
            <td class="left-column">CCF Total:</td>
            <td class="left-text-boxes">@Html.TextBox("txtCCFTotal", @CCFTotal.ToString("F"), new { @class = "txtContext" })</td>
            <td class="right-label">Total Therms:</td>
            <td>@Html.TextBox("txtTotalTherms", @totalTherms.ToString("F"), new { @class = "txtContext" })</td>
        </tr>
        <tr>
            <td>Transportation Charges:</td>
            <td>@Html.TextBox("txtTransportationCharges", @transportationCharges.ToString("F"), new { @class = "txtContext" })</td>
            <td>Delivery Total:</td>
            <td>@Html.TextBox("txtDeliveryTotal", @deliveryTotal.ToString("F"), new { @class = "txtContext" })</td>
        </tr>
    </table>
    <div class="horizontal-line"></div>
    <table>
        <tr>
            <td class="left-column">Ditribution Adjust (*0.13086):</td>
            <td class="left-text-boxes">@Html.TextBox("txtDitributionAdjustment", @distributionAdjustment.ToString("F"), new { @class = "txtContext" })</td>
            <td class="right-label">Environment Charges:</td>
            <td>@Html.TextBox("txtEnvironmentCharges", @environmentalCharges.ToString("F"), new { @class = "txtContext" })</td>
        </tr>
        <tr>
            <td>First 50 Therms (*0.5269):</td>
            <td>@Html.TextBox("txtFirst50Therms", @first50Therms.ToString("F"), new { @class = "txtContext" })</td>
            <td>Local/County Taxess:</td>
            <td>@Html.TextBox("txtLocalTaxes", @localTaxes.ToString("F"), new { @class = "txtContext" })</td>
        </tr>
        <tr>
            <td>Over 50 Therms (*0.4995):</td>
            <td>@Html.TextBox("txtOver50Therms", @over50Therms.ToString("F"), new { @class = "txtContext" })</td>
            <td>State Taxess:</td>
            <td>@Html.TextBox("txtStateTaxes", @stateTaxes.ToString("F"), new { @class = "txtContext" })</td>
        </tr>
    </table>
    <div class="horizontal-line"></div>
    <table>
        <tr>
            <td class="left-column">&nbsp;</td>
            <td class="left-text-boxes">&nbsp;</td>
            <td class="right-label">Amount Due:</td>
            <td>@Html.TextBox("txtAmountDue", @amountDue.ToString("F"), new { @class = "txtContext" })</td>
        </tr>
    </table>

    <div class="horizontal-line"></div>

    <p>@strErrorMessage</p>
}

To execute the application to test it, on the main menu, click Debug -> Start Without Debugging:
In the Invoice # text box, type a random number such as 100001
In the Counter Reading Start text box, enter a number such as 214485
In the Counter Reading End text box, enter a number greater than that of the Counter Start, such as 215079
Click the Calculate button:
Close the browser and return to your programming environment
On the main menu, click File -> New -> Project...
In the middle list, click ASP.NET Web Application (.NET Framework).
Change the Name of the project to CountriesStatistics04
Click OK
In the templates list of the New ASP.NET Web Application dialog box, click the MVC icon and click OK
In the Solution Explorer, right-click Controllers -> Add -> New Scaffolded Item...
In the middle frame of the Add Scaffold dialog box, make sure MVC 5 Controller - Empty is selected and click Add
Type Germany to get GermanyController
Click Add

Change the class as follows:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace CountriesStatistics04.Controllers
{
    public class GermanyController : Controller
    {
        // GET: Germany
        public ActionResult Index()
        {
            return View();
        }

        // GET: GermanStates
        public ActionResult GermanStates()
        {
            return View();
        }

        // GET: StateSearch
        public ActionResult StateSearch()
        {
            return View();
        }
    }
}

In the Solution Explorer, under Views, right-click Germany -> Add -> New Scaffolded Item...
In the middle frame of the Add Scaffold dialog box, click MVC 5 View
Click Add
Type StateSearch as the name of the view
Click Add

Change the document as follows:

@{
    ViewBag.Title = "State Search";
}

<h2>Germany: State Search</h2>

@{
    string[] abbreviations = new string[]
    {
        "TH", "SL", "NW", "HH", "RP", "NI", "SH", "BB", "HE", "BE", "ST", "BW", "BY", "SN", "HB", "MV"
    };
    string[] states = new string[]
    {
        "Saarland", "North Rhine-Westphalia", "Thuringia", "Hamburg", "Rhineland-Palatinate", "Lower Saxony", "Schleswig-Holstein", "Brandenburg", "Hesse", "Berlin", "Saxony-Anhalt", "Baden-Württemberg", "Bavaria", "Saxony", "Bremen", "Mecklenburg-Vorpommern"
    };
    int[] areas = new int[]
    {
        16172, 2569, 34085, 755, 19853, 47609, 15799, 29479, 21115, 892, 20446, 35752, 70552, 18416, 419, 23180
    };
    string[] capitals = new string[]
    {
        "Saarbrücken", "Düsseldorf", "Erfurt", "", "Mainz","Hanover", "Kiel", "", "Wiesbaden", "Stuttgart", "Magdeburg", "Munich", "Potsdam", "Dresden", "Bremen", "Schwerin"
    };
}

@{
    int iArea = 0;
    bool found = false;
    string strErrorMessage = "";
    string strCapital = string.Empty;
    string strStateName = string.Empty;
    string strAbbreviation = string.Empty;
    string strStateLetters = string.Empty;

    if (IsPost)
    {
        
    }
}

@using (Html.BeginForm())
{
    <table style="width: 320px;">
        <tr>
            <td class="left-col">State Letters:</td>
            <td>@Html.TextBox("txtStateLetters", "", new { style = "width: 60px" }) 
              <input type="submit" name="btnFind" value="Find" class="left-col" /></td>
        </tr>
        <tr>
            <td>State:</td>
            <td>@Html.TextBox("txtAbbreviation", @strAbbreviation, new { style = "width: 40px" })
                @Html.TextBox("txtStateName", @strStateName)</td>
        </tr>
        <tr>
            <td>Area:</td>
            <td>@Html.TextBox("txtArea", @iArea, new { @class = "medium-text" }) Km<sup>2</sup></td>
        </tr>
        <tr>
            <td>Capital:</td>
            <td>@Html.TextBox("txtCapital", @strCapital)</td>
        </tr>
    </table>

    <p style="color: red">@strErrorMessage</p>
}

A String With a White Space

A string contains a white space if it was previously initialized with at least one character and all of its characters have been removed or the string was simply initialized with something like the Space bar of the keyboard. Here is an example:

string whiteSpace = "    ";

A Null, Empty, or White-Spaced String

To let you find out whether a string is null or contains a white space, the String class is equipped with a static method named IsNullOrWhiteSpace. Its syntax is:

public static bool IsNullOrWhiteSpace(string value)

Practical Learning: Checking the Nullity of a String

Change the document as follows:

@{
    ViewBag.Title = "State Search";
}

<h2>State Search</h2>

@{
    . . . No Change
}

@{
    int iArea = 0;
    bool found = false;
    string strErrorMessage = "";
    string strCapital = string.Empty;
    string strStateName = string.Empty;
    string strAbbreviation = string.Empty;
    string strStateLetters = string.Empty;

    if (IsPost)
    {
        if (string.IsNullOrWhiteSpace(Request["txtStateLetters"].ToString()))
        {
            strErrorMessage = "You must type a 2-letter abbreviation for a state";
        }
    }
}

@using (Html.BeginForm())
{
    . . . No Change
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
Click the Find button
Close the browser and return to your programming environment

Strings Comparisons

String Equality

The indexed-equivalent characters of two strings can be compared to know whether one is lower or higher than the other's. If you are only interested to know whether two strings are equivalent, to assist you with that operation, the string class is equipped with a method named Equals. It is overloaded with various versions. Two versions use the following syntaxes:

public override bool Equals(object obj);
public bool Equals(string value);

When calling one of these versions, use an object object or a string value that calls it. The method takes one argument. The variable that calls the method is compared to the value passed as argument. If both values are the exact same, the method returns true. The comparison is performed considering the case of each character. If you don't want to consider the case, use the following version of the method:

public bool Equals(string value, StringComparison comparisonType);

An alternative to the second syntax is to use a static version of this method whose syntax is:

public static bool Equals(string a, string b);

This method takes two string arguments and compares them. If they are the same, the method returns true. This method considers the cases of the characters. If you don't want this factor taken into consideration, use the following version of the method:

public static bool Equals(string a,
			              string b,
    			          StringComparison comparisonType);

Practical Learning: Comparing Two Strings for Equality

Change the StateSearch.cshtml document as follows:

@{
    ViewBag.Title = "State Search";
}

<h2>State Search</h2>

@{
    string[] abbreviations = new string[]
    {
        "TH", "SL", "NW", "HH", "RP", "NI", "SH", "BB", "HE", "BE", "ST", "BW", "BY", "SN", "HB", "MV"
    };
    string[] states = new string[]
    {
        "Saarland", "North Rhine-Westphalia", "Thuringia", "Hamburg", "Rhineland-Palatinate", "Lower Saxony", "Schleswig-Holstein", "Brandenburg", "Hesse", "Berlin", "Saxony-Anhalt", "Baden-Württemberg", "Bavaria", "Saxony", "Bremen", "Mecklenburg-Vorpommern"
    };
    int[] areas = new int[]
    {
        16172, 2569, 34085, 755, 19853, 47609, 15799, 29479, 21115, 892, 20446, 35752, 70552, 18416, 419, 23180
    };
    string[] capitals = new string[]
    {
        "Saarbrücken", "Düsseldorf", "Erfurt", "", "Mainz","Hanover", "Kiel", "", "Wiesbaden", "Stuttgart", "Magdeburg", "Munich", "Potsdam", "Dresden", "Bremen", "Schwerin"
    };
}

@{
    int iArea = 0;
    bool found = false;
    string strErrorMessage = "";
    string strCapital = string.Empty;
    string strStateName = string.Empty;
    string strAbbreviation = string.Empty;
    string strStateLetters = string.Empty;

    if (IsPost)
    {
        if (string.IsNullOrWhiteSpace(Request["txtStateLetters"].ToString()))
        {
            strErrorMessage = "You must type a 2-letter abbreviation for a state";
        }
        else
        {
            strStateLetters = Request["txtStateLetters"].ToString();

            for (int i = 0; i < 16; i++)
            {
                if (strStateLetters.Equals(abbreviations[i]))
                {
                    iArea = areas[i];
                    strStateName = states[i];
                    strCapital = capitals[i];
                    strAbbreviation = abbreviations[i];

                    found = true;
                    break;
                }
            }
        }

        if(found == false)
        {
            strErrorMessage = "There is no state with those letters.";
        }
    }
}

@using (Html.BeginForm())
{
    <table style="width: 320px;">
        <tr>
            <td class="left-col">State Letters:</td>
            <td>@Html.TextBox("txtStateLetters", "", new { style = "width: 60px" }) 
              <input type="submit" name="btnFind" value="Find" class="left-col" /></td>
        </tr>
        <tr>
            <td>State:</td>
            <td>@Html.TextBox("txtAbbreviation", @strAbbreviation, new { style = "width: 40px" })
                @Html.TextBox("txtStateName", @strStateName)</td>
        </tr>
        <tr>
            <td>Area:</td>
            <td>@Html.TextBox("txtArea", @iArea, new { @class = "medium-text" }) Km<sup>2</sup></td>
        </tr>
        <tr>
            <td>Capital:</td>
            <td>@Html.TextBox("txtCapital", @strCapital)</td>
        </tr>
    </table>

    <p>@strErrorMessage</p>
}

To execute, on the main menu, click Debug -> Start Without Debugging
In the top text box, type two uppercase letters such as SH
Click the Find button
Close the browser and return to your programming environment
To open a previous project, on the main menu, click File -> Recent Projects and Solutions -> GasUtilityCompany4

String Integral Comparison

String comparison consists of examining the characters of two strings with a character of one string compared to a character of the other string with both characters at the same positions. To support this operation, the string class is equipped with the Compare() method that is overloaded with many versions. One of the versions uses the following syntax:

public static int Compare(string String1, string  String2);

This method is declared static and it takes two arguments. The method returns

A negative value if string1 is less than string2
0 if string1 and string2 are equal
A positive value if string1 is greater than string2

Here is an example:

@{
    string firstName1 = "Andy";
    string lastName1 = "Stanley";
    string firstName2 = "Charles";
    string lastName2 = "Stanley";

    int Value1 = string.Compare(firstName1, firstName2);
    int Value2 = string.Compare(firstName2, firstName1);
    int Value3 = string.Compare(lastName1, lastName2);
}

When using this version of the string.Compare() method, the case (upper or lower) of each character is considered. If you don't want to consider this factor, the String class proposes another version of the method. Its syntax is:

public static int Compare(string String1, string String2, bool ignoreCase);

The third argument allows you to ignore the case of the characters when performing the comparison.

Practical Learning: Integrally Comparing Strings

Access the AccountCreation.cshtml file and change its document as follows:

@{
    ViewBag.Title = "Employee  Account Creation";
}

<h2>Employee Account Creation</h2>

<div class="horizontal-line"></div>

@{
    int length = 0;
    int digits = 0;
    int symbols = 0;
    int lowercase = 0;
    int uppercase = 0;
    string strUsername = string.Empty;
    string strLastName = string.Empty;
    string strFirstName = string.Empty;
    string strMiddleName = string.Empty;
    string strNewPassword = string.Empty;
    string strErrorMessage = string.Empty;
    string strConfirmPassword = string.Empty;

    if (IsPost)
    {
        strNewPassword = Request["txtNewPassword"].ToString();
        length = strNewPassword.Length;
        strConfirmPassword = Request["txtConfirmPassword"].ToString();

        for (int i = 0; i < length; i++)
        {
            if (Char.IsDigit(strNewPassword[i]))
            {
                digits++;
            }

            if (Char.IsSymbol(strNewPassword[i]) || Char.IsPunctuation(strNewPassword[i]))
            {
                symbols++;
            }

            if (Char.IsLower(strNewPassword[i]))
            {
                lowercase++;
            }

            if (Char.IsUpper(strNewPassword[i]))
            {
                uppercase++;
            }
        }
        
        if (string.Compare(strNewPassword, strConfirmPassword) == 0)
        {
            strErrorMessage = "Your password will be saved successfully.";
        }
        else
        {
            strErrorMessage = "The passwords don't match.";
        }
    }
}

@using (Html.BeginForm())
{
    <table>
        <tr>
            <td class="left-col">First Name:</td>
            <td>@Html.TextBox("txtFirstName", @strFirstName)</td>
        </tr>
        <tr>
            <td>Middle Name:</td>
            <td>@Html.TextBox("txtMiddleName", @strMiddleName)</td>
        </tr>
        <tr>
            <td>Last Name:</td>
            <td>@Html.TextBox("txtLastName", @strLastName)</td>
        </tr>
        <tr>
            <td>Username:</td>
            <td>@strUsername</td>
        </tr>
    </table>
    <div class="horizontal-line"></div>
    <table>
        <tr>
            <td class="left-col">New Password:</td>
            <td>@Html.TextBox("txtNewPassword", @strNewPassword)</td>
            <td>@Html.TextBox("txtCharacters", @length, new { @class = "small-text" }) Characters</td>
        </tr>
        <tr>
            <td>Confirm Password:</td>
            <td>@Html.TextBox("txtConfirmPassword", @strConfirmPassword)</td>
            <td>&nbsp;</td>
        </tr>
    </table>
    <table>
        <tr>
            <td class="left-col">&nbsp;</td>
            <td class="large">@Html.TextBox("txtLowercase", @lowercase, new { @class = "small-text" }) Lowercase Letters</td>
            <td>@Html.TextBox("txtUppercase", @uppercase, new { @class = "small-text" }) Uppercase Letters</td>
        </tr>
        <tr>
            <td class="left-col">&nbsp;</td>
            <td>@Html.TextBox("txtDigits", @digits, new { @class = "small-text" }) Digits</td>
            <td>@Html.TextBox("txtSymbols", @symbols, new { @class = "small-text" }) Symbols</td>
        </tr>
    </table>
    <div class="horizontal-line"></div>
    <p class="text-center"><input type="submit" name="btnSubmit" value="Submit" class="btnLarge" /></p>
    <div class="horizontal-line"></div>

    <p>@strErrorMessage</p>
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
In the New Password text box, type something, such as $0uthD@koTA1889 and press Tab/li>
In the Confirm Password text box, type something different, such as $outhD@KoTA1889
Click the Submit button:
Type the same passwords in both text boxes
Click the Submit button
Close the browser and return to your programming environment
On the main menu of Microsoft Visual Studio, click File -> New Project...
In the New Project dialog box, make sure ASP.NET Web Application (.NET Framework) is selected in the middle list.
Change the Name of the project to Chemistry10
Click OK
In the New ASP.NET Web Application, make sure the MVC icon is selected in the templates list.
Click OK
In the Solution Explorer, right-click Chemistry10-> Add -> Add ASP.NET Folder -> App_Code
In the Solution Explorer, right-click App_Code -> Add -> Class
Type the name of the file as Element
Click Add

Populate the document as follows:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Chemistr09.App_Code
{
    public enum Phase
    {
        Gas,
        Liquid,
        Solid,
        Unknown
    }

    public class Element
    {
        public string Symbol       { get; set; } = "";
        public string ElementName  { get; set; } = "";
        public int    AtomicNumber { get; set; } = 0;
        public float  AtomicWeight { get; set; } = 0.000F;
        public Phase  Phase        { get; set; } = Phase.Unknown;

        public Element()
        {
        }

        public Element(int number)
        {
            AtomicNumber = number;
        }

        public Element(string symbol)
        {
            Symbol = symbol;
        }

        public Element(int number, string symbol, string name, float mass)
        {
            Symbol = symbol;
            ElementName = name;
            AtomicWeight = mass;
            AtomicNumber = number;
        }
    }
}

In the Solution Explorer, expand Controllers and double-click HomeController.cs to open it

Add three new methods as follows:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace Chemistry10.Controllers
{
    public class HomeController : Controller
    {
        // GET: Home
        public ActionResult Index()
        {
            return View();
        }

        public ActionResult About()
        {
            ViewBag.Message = "Your application description page.";

            return View();
        }

        public ActionResult Contact()
        {
            ViewBag.Message = "Your contact page.";

            return View();
        }

        // GET: ElementSearch
        public ActionResult ElementSearch()
        {
            return View();
        }

        // GET: Compounds
        public ActionResult Compounds()
        {
            return View();
        }

        // GET: PeriodicTable
        public ActionResult PeriodicTable()
        {
            return View();
        }
    }
}

In the Solution Explorer, expand Views, right-click Home -> Add -> New Scaffolded Item...
In the middle frame of the Add Scaffold dialog box, click MVC 5 View
Click Add
In the Add View dialog box, type Compounds for the View Name
Click Add

Change the document as follows:

@{
    ViewBag.Title ="Chemical Compounds";
}

<h2 class="text-center">Chemical Compounds</h2>

In the Solution Explorer, right-click Home -> Add -> View...
Type PeriodicTable for the View Name
Click Add

Change the document as follows:

@{
    ViewBag.Title = "Periodic Table";
}

<h2 class="text-center">Periodic Table</h2>

String-Case Conversions

Converting a String to Lowercase

To let you convert a string from lowercase to uppercase, the String class is equipped with a method named ToLower. It is overloaded with two versions. One of the versions of this method uses the following syntax:

public string ToLower()

This method considers each character of the string that called it. If the character is already in uppercase, it would not change. If the character is a lowercase alphabetic character, it would be converted to uppercase. If the character is not an alphabetic character, it would be kept "as-is".

Practical Learning: Converting a String to Lowercase

In the Solution Explorer, right-click Home -> Add -> View...
In the Add View dialog box, change the View Name to ElementSearch
Click Add

To create and process a form, change the document as follows:

@{
    ViewBag.Title = "Element Search";
}

<h2>@ViewBag.SubTitle</h2>

@{
    Chemistry10.App_Code.Element selected = new Chemistry10.App_Code.Element();

    Chemistry10.App_Code.Element  H = new Chemistry10.App_Code.Element(1,  "H", "Hydrogen", 1.008F) { Phase = Chemistry10.App_Code.Phase.Gas };
    Chemistry10.App_Code.Element He = new Chemistry10.App_Code.Element(2, "He", "Helium", 4.002602F) { Phase = Chemistry10.App_Code.Phase.Gas };
    Chemistry10.App_Code.Element Li = new Chemistry10.App_Code.Element(3, "Li", "Lithium", 6.94F) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element Be = new Chemistry10.App_Code.Element(4, "Be", "Beryllium", 9.0121831F) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element  B = new Chemistry10.App_Code.Element(5,  "B", "Boron", 10.81F) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element  C = new Chemistry10.App_Code.Element(name: "Carbon", mass: 12.011F, symbol: "C", number: 6) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element  N = new Chemistry10.App_Code.Element(7, "N", "Nitrogen", 14.007F) { Phase = Chemistry10.App_Code.Phase.Gas };
    Chemistry10.App_Code.Element  O = new Chemistry10.App_Code.Element(8, "O", "Oxygen", 15.999F) { Phase = Chemistry10.App_Code.Phase.Gas};
    Chemistry10.App_Code.Element  F = new Chemistry10.App_Code.Element(9, "F", "Fluorine", 15.999F) { Phase = Chemistry10.App_Code.Phase.Gas };
    Chemistry10.App_Code.Element Ne = new Chemistry10.App_Code.Element("Ne") { AtomicNumber = 10, ElementName = "Neon", AtomicWeight = 20.1797F, Phase = Chemistry10.App_Code.Phase.Gas };
    Chemistry10.App_Code.Element Na = new Chemistry10.App_Code.Element(11, "Na", "Sodium", 22.98976928F) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element Mg = new Chemistry10.App_Code.Element(12, "Mg", "Magnesium", 24.305F) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element Al = new Chemistry10.App_Code.Element(13, "Al", "Aluminium", 26.9815385F) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element Si = new Chemistry10.App_Code.Element() { ElementName = "Silicon", AtomicWeight = 28.085F, Symbol = "Si", AtomicNumber = 14, Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element  P = new Chemistry10.App_Code.Element() { ElementName = "Phosphorus", AtomicWeight = 30.973761998F, Symbol = "P", AtomicNumber = 15, Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element  S = new Chemistry10.App_Code.Element(16, "S", "Sulfur", 32.06F) { Phase = Chemistry10.App_Code.Phase.Solid };
    Chemistry10.App_Code.Element Cl = new Chemistry10.App_Code.Element(17, "Cl", "Chlorine", 35.45F) { Phase = Chemistry10.App_Code.Phase.Gas };
    Chemistry10.App_Code.Element Ar = new Chemistry10.App_Code.Element(18, "Ar", "Potassium", 39.098F) { Phase = Chemistry10.App_Code.Phase.Solid };

    string strSymbolEntered = "";

    if (IsPost)
    {
        strSymbolEntered = Request["txtSymbolEntered"].ToLower();

        switch (strSymbolEntered)
        {
            case "h":
                selected = H;
                break;
            case "he":
                selected = He;
                break;
            case "li":
                selected = Li;
                break;
            case "be":
                selected = Be;
                break;
            case "b":
                selected = B;
                break;
            case "c":
                selected = C;
                break;
            case "n":
                selected = N;
                break;
            case "o":
                selected = O;
                break;
            case "f":
                selected = F;
                break;
            case "ne":
                selected = Ne;
                break;
            case "na":
                selected = Na;
                break;
            case "mg":
                selected = Mg;
                break;
            case "al":
                selected = Al;
                break;
            case "si":
                selected = Si;
                break;
            case "p":
                selected = P;
                break;
            case "s":
                selected = S;
                break;
            case "cl":
                selected = Cl;
                break;
            case "ar":
                selected = Ar;
                break;
        }

        ViewBag.SubTitle = selected.ElementName;
    }
}

<div class="sub-title-holder">
    <div id="sub-title">@ViewBag.SubTitle</div>
    <hr />
</div>

<div class="elm-presentation">
    @using (Html.BeginForm())
    {
        <table>
            <tr>
                <td class="emphasize">Enter symbol:</td>
                <td>
                    @Html.TextBox("txtSymbolEntered", @strSymbolEntered, new { @class = "small-text" }) 
                    <input type="submit" name="btnFind" value="Find" style="width: 70px;" />
                </td>
            </tr>
            <tr>
                <td class="emphasize">Symbol:</td>
                <td>@Html.TextBox("txtSymbol", @selected.Symbol)</td>
            </tr>
            <tr>
                <td class="emphasize">Element Name:</td>
                <td>@Html.TextBox("txtElementName", @selected.ElementName)</td>
            </tr>
            <tr>
                <td class="emphasize">Atomic Weight:</td>
                <td>@Html.TextBox("txtAtomicWeight", @selected.AtomicWeight)</td>
            </tr>
            <tr>
                <td class="emphasize">Phase:</td>
                <td>@Html.TextBox("txtAtomicWeight", @selected.Phase)</td>
            </tr>
        </table>
    }
</div>

To exectue the project, on the main menu, click Debug -> Start Without Debugging
Type a one or two-letter chemical symbol. Here is an example:
Click the Find button:
Type another symbol such as na
Click the Find button:
Close the browser and return to your programming environment
To open a previous project, on the main menu, click File -> Recent Projects and Solutions -> CountriesStatistics04
In the top text box, type nw
Click the Find button
Close the browser and return to your programming environment

Converting a String to Uppercase

To let you convert a string to uppercase, the String class is equipped with a method named ToUpper. This method is overloaded with two versions. The syntax of one of the versions is:

public string ToUpper()

Here is an example:

@{
    string strFullName   = "Alexander Patrick Katts";
    string strConversion = strFullName.ToUpper();
}

Practical Learning: Converting a String to Uppercase

Access the StateSearch.cshtml file and change its code as follows:

@{
    ViewBag.Title = "State Search";
}

<h2>Germany: State Search</h2>

@{
    . . .  No Change
}

@{
    int iArea = 0;
    bool found = false;
    string strErrorMessage = "";
    string strCapital = string.Empty;
    string strStateName = string.Empty;
    string strAbbreviation = string.Empty;
    string strStateLetters = string.Empty;

    if (IsPost)
    {
        if (string.IsNullOrWhiteSpace(Request["txtStateLetters"].ToString()))
        {
            strErrorMessage = "You must type a 2-letter abbreviation for a state";
        }
        else
        {
            strStateLetters = Request["txtStateLetters"].ToString().ToUpper();

            for (int i = 0; i < 16; i++)
            {
                if (strStateLetters.Equals(abbreviations[i]))
                {
                    iArea = areas[i];
                    strStateName = states[i];
                    strCapital = capitals[i];
                    strAbbreviation = abbreviations[i];

                    found = true;
                    break;
                }
            }
        }

        if (found == false)
        {
            strErrorMessage = "There is no state with those letters.";
        }
    }
}

@using (Html.BeginForm())
{
    . . . No Change
}

To execute the project, on the main menu, click Debug -> Start Without Debugging
In the top text box, type nw
Click the Find button
In the top text box, type S. L.
Click the Find button
Close the browser and return to your programming environment


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