Tutorial Series: Free C# Fundamentals via ASP.NET Web Apps
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This lesson will cover how to format strings. We already looked at how to concatenate strings, with the “+” and “+=” operators, but this lesson will show you how to handle special formatting conditions, such as the patterns seen in things like phone, social security, or credit card numbers. These all have some form of patterned formatting, or otherwise have some special arrangement of numbers and characters.
We’ll demonstrate this with a very simple loan application form that stores pieces of information like the phone number, social security number, salary and date. It will then display all of this information back to resultLabel with special formatting so that it looks presentable. Begin this lesson by creating a new ASP.NET project called “CS-ASP_019,” and set up a Default.aspx with the following Server Controls, and programmatic IDs:
nameTextBox
phoneTextBox
ssTextBox
loanDateCalendar
salaryTextBox
submitButton
resultLabel
The first thing we will want to do is take the applicant's name that was input via nameTextBox, and output it within a formal “thank you” statement:
This approach uses the string concatenation technique we have become familiar with. This will get the job done, but isn’t as readable owing to the multiple uses of the concatenation operator. A much more readable way of achieving this is by calling the string.Format() method instead:
This method takes in (1) a literal string argument, along with a (2) variable string argument, and then using a (3) special placeholder it transposes the variable string argument into the placeholder position within the literal string:
Note: This placeholder system is zero-based, meaning that the first value passed in will be {0}, then {1}, {2} {3}, etc.
The output when running the application will look like this:
This essentially produces a string “template” with as many placeholders as needed:
The problem now is that the entered number itself should be formatted to look more like a typical Social Security number. We start by converting this value to an integer using int.Parse(), and then storing it into an integer variable:
Modify the string.Format() method to take this int value and apply to it a formatting pattern of number sequences delimited by dashes. Here we took the {1} placeholder and appended to it a formatting pattern, with a colon separating the placeholder from its pattern:
The formatting pattern will become much more apparent when running the application:
Tip: You should note that phone numbers are at least 10 digits in length, which reaches the upper-limits allowable for storage into an int variable. If the first digit in the phone number is greater than 1, there is a good chance it will cross the allowable threshold and return an error. To fix this, you can store the number into a long. However, if the application ends up processing thousands of numbers (or more) this could be very inefficient and you would probably want to leave the phone number as a string.
You can also inject HTML straight into the output string, considering that the output is ultimately being delivered through the browser. Here, we injected a simple HTML line break tag “<br />” to put each phrase onto its own line:
Now, let’s apply the same principles towards formatting the phone number. Add a third placeholder, {2}, which will take the value supplied in yet another argument, phone. We will be applying this process over and over again, to handle the other user inputs, which will lead to a very long statement. To make it more readable, we can use the concatenation operator to break up the statement on separate lines:
The end result will look like this:
Tip: This goes back to the previous lesson on code style. This is very subjective - what looks good to one person, may not look good to another. Here’s a good rule of thumb: keep lines approximately within an 80-column range. You can find the column number for each line at the bottom right of Visual Studio. Also, when separating lines, try to keep a logical separator in mind. Here, the <br /> tag is used as a line separator, as well as the comma after each string argument. This sets a pattern that makes it easier for you to get a sense of what the code is doing, at a glance.
Next we will want to format the date returned by the applicant’s Calendar selection. We already saw built-in formatting methods like ToShortDateString(), but sometimes that isn’t flexible enough to handle a particular formatting requirement. Below is a short list of available date formatting options in C#:
This is a partial list that can be found by visiting:
Here we are applying some of these special date formatting rules to the fourth placeholder at {3}, which formats the date given by loanDateCalendar.SelectedDate:
This produces the date formatting shown here:
When working with currency you can place a “C” after the colon, inside the placeholder, to tell the compiler that this is to be formatted as a currency. If you want to allow for cents, you need to first convert the entered value to a double, as well:
For more information on currency formatting options, visit the following page showing you a variety of ways to represent exponential values, fixed point, and other numeric types of values:
http://is.gd/formattingcurrency
Formatting strings is very useful and powerful for you, the developer, when creating forms for users to fill out. Keep these tools in mind, as they are going to be utilized in the next Challenge coming up very soon.
Lesson 1 - Series Introduction
Lesson 2 - Installing Visual Studio 2015
Lesson 3 - Building Your First Web App
Lesson 4 - Understanding What You Just Did
Lesson 5 - Working with Projects in Visual Studio
Lesson 6 - Simple Web Page Formatting in Visual Studio
Lesson 7 - Variables and Data Types
Lesson 8 - Data Type Conversion
Lesson 9 - Arithmetic Operators
Challenge 2 - ChallengeSimpleCalculator
Solution - ChallengeSimpleCalculator
Lesson 11 - Conditional If Statements
Lesson 12 - The Conditional Ternary Operator
Challenge 3 - ChallengeConditionalRadioButton
Solution - Challenge Conditional RadioButton
Lesson 13 - Comparison and Logical Operators
Lesson 13 Challenge - First Papa Bob's Website
Solution - Challenge First Papa Bob's Website
Lesson 14 - Working with Dates and Times
Lesson 15 - Working With Spans of Time
Lesson 16 - Working with the Calendar Server Control
Challenge 4 - Challenge Days Between Dates
Solution - Challenge Days Between Dates
Lesson 17 - Page_Load and Page.IsPostBack
Lesson 18 - Setting a Break Point and Debugging
Lesson 19 - Formatting Strings
Challenge 5 - Challenge Epic Spies Assignment
Solution - Challenge Epic Spies Assignment
Lesson 20 - Maintaining State with ViewState
Lesson 21 - Storing Values in Arrays
Lesson 22 - Understanding Multidimensional Arrays
Lesson 23 - Changing the Length of an Array
Challenge 6 - Challenge Epic Spies Asset Tracker
Solution - Challenge Epic Spies Asset Tracker
Lesson 24 - Understanding Variable Scope
Lesson 25 - Code Blocks and Nested If Statements
Lesson 26 - Looping with the For Iteration Statement
Challenge 7 - Challenge For Xmen Battle Count
Solution - Challenge For Xmen Battle Count
Lesson 27 - Looping with the while() & do...while() Iteration Statements
Lesson 28 - Creating and Calling Simple Helper Methods
Lesson 29 - Creating Methods with Input Parameters
Lesson 30 - Returning Values from Methods
Lesson 31 - Creating Overloaded Methods
Lesson 32 - Creating Optional Parameters
Lesson 33 - Creating Names Parameters
Lesson 34 - Creating Methods with Output Parameters
Challenge 8 - Challenge Postal Calculator Helper Methods
Solution - Challenge Postal Calculator Helper Methods
Solution - Mega Challenge Casino
Lesson 35 - Manipulating Strings
Challenge 9 - Phun With Strings
Solution - Challenge Phun With Strings
Lesson 36 - Introduction to Classes and Objects
Challenge - Hero Monster Classes Part 1
Solution - Hero Monster Classes Part 1
Challenge - Hero Monster Classes Part 2
Solution - Challenge Hero Monster Classes Part 2
Lesson 37 - Creating Class Files Creating Cohesive Classes and Code Navigation
Lesson 38 - Understanding Object References and Object Lifetime
Lesson 39 - Understanding the .NET Framework and Compilation
Lesson 40 - Namespaces and Using Directives
Lesson 41 - Creating Class Libraries and Adding References to Assemblies
Lesson 42 - Accessibility Modifiers, Fields and Properties
Lesson 43 - Creating Constructor Methods
Lesson 44 - Naming Conventions for Identifiers
Lesson 45 - Static vs Instance Members
Challenge 10 - Challenge Simple Darts
Solution - Challenge Simple Darts
Lesson 46 - Working with the List Collection
Lesson 47 - Object Initializers
Lesson 48 - Collection Initializers
Lesson 49 - Working with the Dictionary Collection
Lesson 50 - Looping with the foreach Iteration Statement
Lesson 51 - Implicitly-Typed Variables with the var Keyword
Challenge 11 - Challenge Student Courses
Solution - Challenge Student Courses
Lesson 53 - Working with Enumerations
Lesson 54 - Understanding the switch() Statement
Lesson 55 - First Pass at the Separation of Concerns Principle
Lesson 56 - Understanding Exception Handling
Lesson 57 - Understanding Global Exception Handling
Lesson 58 - Understanding Custom Exceptions
Lesson 59 - Creating a Database in Visual Studio
Lesson 60 - Creating an Entity Data Model
Lesson 61 - Displaying the DbSet Result in an ASP.NET GridView
Lesson 62 - Implementing a Button Command in a GridView
Lesson 63 - Using a Tools-Centric Approach to Building a Database Application
Lesson 64 - Using a Maintenance-Driven Approach to Building a Database Application
Lesson 65 - Creating a New Instance of an Entity and Persisting it to the Database
Lesson 66 - Package Management with NuGet
Lesson 67 - NuGet No-Commit Workflow
Lesson 68 - Introduction the Twitter Bootstrap CSS Framework
Lesson 69 - Mapping Enum Types to Entity Properties in the Framework Designer
Lesson 70 - Deploying the App to Microsoft Azure Web Services Web Apps
Papa Bob's Mega Solution Part 1 - Setting up the Solution
Papa Bob's Mega Solution Part 2 - Adding an Order to the Database
Papa Bob's Mega Solution Part 3 - Passing an Order from the Presentation Layer
Papa Bob's Mega Solution Part 4 - Creating the Order Form
Papa Bob's Mega Solution Part 5 - Adding Enums
Papa Bob's Mega Solution Part 6 - Creating an Order with Validation
Papa Bob's Mega Solution Part 7 - Calculating the Order Price
Papa Bob's Mega Solution Part 8 - Displaying the Price to the User
Papa Bob's Mega Solution Part 9 - Creating the Order Management Page