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Beginning C# 7 Hands-On ??? Advanced Language Features
Beginning C# 7 Hands-On ??? Advanced Language Features

Beginning C# 7 Hands-On ??? Advanced Language Features: Learn the advanced-level features of C# 7 using Visual Studio 2017

By Tom Owsiak
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Book Oct 2017 310 pages 1st Edition
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Beginning C# 7 Hands-On ??? Advanced Language Features

Chapter 1. Creating a Simple Generics Class

In this chapter, you will look at the basics of making a simple generic class so that one class can operate on many different data types. A great benefit of generics is flexibility.

Creating a generics class


Bring up a project, and go to Solution Explorer; right-click, select Add, and click on Class. Name the class GenericsClass; a simple generics class. Then, click on OK. When the Visual Studio message comes up, click on Yes.

For our purposes, you don't need any of the using System lines at the top, nor any of the comments underneath, so delete them. Your initial screen should look like Figure 1.1.1:

Figure 1.1.1: The initial GenericsClass.cs screen

Working with different data types

Now, let's put a <T> symbol after where it says public class GenericsClass, as follows:

public class GenericsClass<T>

This means that this single class can work equally well with several different data types. Next, enter the following beneath the open curly brace under the preceding line:

private T[] vals;

Enter the following comment directly above this line:

//generic array instance variable

In other words, this will operate equally well on doubles, decimals, integers, and so on.

Making parameters that are generic

Now, in the following line, enter the following:

public GenericsClass(T[] input)

As you can see, you can also make parameters that are generic like this one. This is a parameter, input is the name of it, and the type is T. So, it's a generic array.

Next, enter the following between a set of curly braces beneath the preceding line:

vals = input;

Displaying the values

Of course, you should be able to display these values. so, enter the following line beneath the closed curly brace under the vals = input; line:

public string DisplayValues()

To display these values, you'll enter the following between a set of curly braces beneath the preceding line.

First, put in a string, as follows:

string str = null;

Next, declare the string and initialize the value to null.

Then, enter the following directly below this line:

foreach ( T t in vals)

As you can see, the foreach loop here is going to operate. The T object will be a different data type, depending on how we choose to make the object. The t variable, of course, is each specific value inside the vals array.

Next, you will enter the following between a set of curly braces beneath the preceding line:

str += $"<br>Value={t}";

Remember, we use the += operator to accumulate and <br> to push down to the next line. To get the value, of course, we will put in the t variable.

At the end, you want to return this, so you will type the following beneath the closed curly brace under the preceding line:

return str;

That's it. The final version of the GenericsClass.cs file for this chapter, including comments, is shown in the following code block:

//<T> means this class can operate on many different data types
public class GenericsClass<T>
{
    //generic array instance variable
    private T[] vals;//array of T inputs
    public GenericsClass(T[] input)
    {
        //set value of instance variable
        vals = input;
    }
    public string DisplayValues()
    {
        string str = null;//create string to build up display
        foreach(T t in vals)
        {
            //actually accumulate stuff to be displayed
            str += $"<br>Value={t}";
        }
    //return string of outputs to calling code
    return str;
    }
}

Notice that we have a single block of code; this will now operate on integers, doubles, and so on.

Adding a button to Default.aspx


Now, let's take a look at Default.aspx. The only thing we really need to do at this time is to add a Button control. For this, go to Toolbox and grab a Button control from there. Drag and drop it below the line beginning with <form id=... (you can delete the <div> lines, as we won't be needing them). Change the text on the Button control to, for example, Display Values. Your complete Default.aspx file should look like the one shown in Figure 1.1.2:

Figure 1.1.2: The complete HTML for this project

Now, go to the Design view. Our very simple interface is shown in Figure 1.1.3:

Figure 1.1.3: Our very simple interface in the Design view

Initializing a collection of integers to their array and displaying the results


Now, double-click on the Display Values button and go into Default.aspx.cs. Delete the Page_Load block. Next, between the set of curly braces beneath the line beginning with protected void Button1_Click..., enter the following:

GenericsClass<int> ints = new GenericsClass<int>(new int[] { 1, 2, 3, 4, 5 });

You can see in this line that we are basically initializing a collection of integers to their array.

Now, you can display this. So, for example, you can enter the following below this line:

sampLabel.Text += ints.DisplayValues();

Notice that the GenericsClass which we have constructed is operating in integers, but it can operate equally well on any other data type.

Changing the data types in our generics class

Now, to make the code efficiency more obvious, take both of the preceding lines, copy them (Ctrl + C) and paste them (Ctrl + V) beneath these and just change it to double, as follows:

GenericsClass<double> dubs = new GenericsClass<double>(new double[] {1, 2, 3, 4, 5});
sampLabel.Text = ints.DisplayValues();

We'll call this one dubs and change the name here to double: it's the same code, the same class, and the same generic class that you can operate on the doubles. Again, to emphasize this one more time, and to see that flexibility and code reuse is really the purpose here; that is, the ability to reuse code, we'll now take both of these new lines, copy and paste them below once more, and just change double to decimal, as follows:

GenericsClass<decimal> decs = new GenericsClass<decimal>(new decimal[] { 1, 2, 3, 4, 5 });
sampLabel.Text = ints.DisplayValues();

Let's call this one decs. Now, of course, if you want to make things a little more interesting, you can throw in some decimals:

GenericsClass<double> dubs = new GenericsClass<double>(new double[] { 1.0, -2.3, 3, 4, 5 });
sampLabel.Text = ints.DisplayValues();
GenericsClass<decimal> decs = new GenericsClass<decimal>(new decimal[] { 1, 2.0M, 3, 4, 5.79M });
sampLabel.Text = ints.DisplayValues();

Note

With decimals, just make sure that you put the M suffix in there, because you need the M suffix at the end to indicate that it's a decimal.

Running the program

Now, let's take a look. When you run this code and click on the Display Values button, your screen will look like the one shown in Figure 1.1.4:

Figure 1.1.4: The initial run of our code

Accumulating the input

Now, we will accumulate the input. So, in the following sampLabel.Text lines, we change the = sign to +=, as shown here:

GenericsClass<double> dubs = new GenericsClass<double>(new double[] { 1.0, -2.3, 3, 4, 5 });
sampLabel.Text += ints.DisplayValues();
GenericsClass<decimal> decs = new GenericsClass<decimal>(new decimal[] { 1, 2.0M, 3, 4, 5.79M });
sampLabel.Text += ints.DisplayValues();

Let's run it one more time. Click on theDisplay Values button and your screen will now look like the one shown in Figure 1.1.5:

Figure 1.1.5: The input is now being accumulated, and the values are showing as expected

The program is now working as expected.

So, the big idea of generics at this point is that you can define a generic class. This class can operate equally well on many different data types. For example, you can make a generic class that operates on integers as well as on doubles and decimals.

Note

This step isn't strictly required, but here's a little bit of additional insight. If you want to, you can set a breakpoint as follows. Select the line with the open curly brace under the line beginning with protected void Button1_Click.... Now, go to Debug |Step Into (F11) and click on Display Values.

Now, we will go through it. So, to first step into it, hover your mouse over the T object in the following line in Generics Class.cs:

public GenericsClass(T[] input)

Here, T is essentially like a parameter, so it does have a certain value, which is expressed in the vals = input; line. The first time, T is used for integers. This is how you can step through this code. At the bottom of the screen, the values inside the array are displayed, as shown in Figure 1.1.6:

Figure 1.1.6: The values inside the array

The t variable, as you can see in Figure 1.1.7, is an integer, and this is how it operates:

Figure 1.1.7: The t is an integer

Notice also in the screenshot that it's a generics class with an <int> datatype.

The T object in the foreach(T t in vals) line right now represents an integer, and so on for the other data types. So, flexibility of code and reuse of code means that you will write less code. If not for generics, you would have to create individual classes to handle each different data type.

Chapter review


For review, the complete version of the Default.aspx.cs file for this chapter, including comments, is shown in the following code block:

//using is a directive
//System is a name space
//name space is a collection of features that our needs to run
using System;
//public means accessible anywhere
//partial means this class is split over multiple files
//class is a keyword and think of it as the outermost level of grouping
//:System.Web.UI.Page means our page inherits the features of a Page
public partial class _Default : System.Web.UI.Page
{
    protected void Button1_Click(object sender, EventArgs e)
    {
        //in each case below, GenericsClass<...> works equally well with
        //integers, doubles and decimals, among others
        GenericsClass<int> ints = new GenericsClass<int>(new int[] { 1, 2, 3, 4, 5 });
        sampLabel.Text = ints.DisplayValues();
        GenericsClass<double> dubs = new GenericsClass&lt;double>(new double[] { 1.0, -2.3, 3, 4, 5 });
        sampLabel.Text += ints.DisplayValues();
        GenericsClass<decimal> decs = new GenericsClass<decimal>(new decimal[] { 1, 2.0M, 3, 4, 5.79M });
        sampLabel.Text += decs.DisplayValues();
    }
} 

Summary


In this chapter, you learned about the basics of making a simple generic class, so that one class can operate on many different data types. A great benefit of generics is flexibility. You created a simple generics class that worked with different data types, made generic parameters, initialized a collection of integers to their array and displayed the results, and then changed the data types in the generics class to doubles and decimals.

In the next chapter, you will learn about generic methods, or methods that can operate on different data types. You will also learn about constraining a method in terms of the data types that it can operate on, so we'll add a concept called constraints.

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Key benefits

  • • Learn C#, Visual Studio, and object-oriented programming
  • • Get practical examples of advanced C# language features so that you can easily master them yourself
  • • Use the C# programming language to work generics and lambda expressions
  • • Program C# and SQL Server 2017
  • • Get ready for your first MVC applications

Description

Beginning C# 7 Hands-On – Advanced Language Features assumes that you’ve mastered the basic elements of the C# language and that you're now ready to learn the more advanced C# language and syntax, line by line, in a working Visual Studio environment. You'll learn how to code advanced C# language topics including generics, lambda expressions, and anonymous methods. You'll learn to use query syntax to construct queries and deploy queries that perform aggregation functions. Work with C# and SQL Server 2017 to perform complex joins and stored procedures. Explore advanced file access methods, and see how to serialize and deserialize objects – all by writing working lines of code that you can run within Visual Studio. This book is designed for beginner C# developers who have mastered the basics now, and anyone who needs a fast reference to using advanced C# language features in practical coding examples. You'll also take a look at C# through web programming with web forms. By the time you’ve finished this book, you’ll know all the critical advanced elements of the C# language and how to program everything from C# generics to XML, LINQ, and your first full MVC web applications. These are the advanced building blocks that you can then combine to exploit the full power of the C# programming language, line by line.

What you will learn

• Learn C# advanced language elements and techniques • Discover advanced C# techniques with hands-on working examples • Build on your knowledge of OOP by using C# generics and lambda expressions • Work with C# and LINQ custom data types • Program C# and SQL Server 2017 to manage and query data • Create your first full MVC application

Product Details

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Publication date : Oct 31, 2017
Length 310 pages
Edition : 1st Edition
Language : English
ISBN-13 : 9781788294263
Vendor :
Microsoft
Category :

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Product feature icon Download this book in EPUB and PDF formats
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Product Details


Publication date : Oct 31, 2017
Length 310 pages
Edition : 1st Edition
Language : English
ISBN-13 : 9781788294263
Vendor :
Microsoft
Category :

Table of Contents

35 Chapters
Title Page Chevron down icon Chevron up icon
Credits Chevron down icon Chevron up icon
About the Author Chevron down icon Chevron up icon
www.PacktPub.com Chevron down icon Chevron up icon
Customer Feedback Chevron down icon Chevron up icon
Preface Chevron down icon Chevron up icon
1. Creating a Simple Generics Class Chevron down icon Chevron up icon
2. Creating a Generic Method Chevron down icon Chevron up icon
3. Implementing a Generic Interface to Accomplish Sorting Chevron down icon Chevron up icon
4. Making Delegates More Flexible with Generics Chevron down icon Chevron up icon
5. Creating and Using Generic Dictionaries Chevron down icon Chevron up icon
6. Connection Between Delegates and Lambda Expressions Chevron down icon Chevron up icon
7. Expression-Bodied Lambdas and Expression-Bodied Members Chevron down icon Chevron up icon
8. Anonymous Methods and Objects That Run Their Own Delegates Chevron down icon Chevron up icon
9. C# with LINQ and Built-In Types Chevron down icon Chevron up icon
10. C# with LINQ and Custom Data Types Chevron down icon Chevron up icon
11. Using Query Syntax to Construct Queries Chevron down icon Chevron up icon
12. Queries That Perform Aggregation Functions Chevron down icon Chevron up icon
13. Using LINQ to Summarize Tuples Chevron down icon Chevron up icon
14. Summarizing Results with Grouping Chevron down icon Chevron up icon
15. Joining Datasets with Inner Joins Chevron down icon Chevron up icon
16. Downloading, Installing, and Running SQL Server 2017 Chevron down icon Chevron up icon
17. Writing Code to Manually Connect to a Table and Retrieve Records Chevron down icon Chevron up icon
18. Inserting Records into Tables Using Stored Procedures Chevron down icon Chevron up icon
19. Using the Nullable Feature to Make Apps More Stable Chevron down icon Chevron up icon
20. Connecting a Chart Control to SQL Server Chevron down icon Chevron up icon
21. Using LINQ to Operate on Tables from SQL Server Chevron down icon Chevron up icon
22. Creating a Page That Saves Text to Disk Chevron down icon Chevron up icon
23. Creating a Page That Uses the File Upload Control Chevron down icon Chevron up icon
24. Serializing and Deserializing Objects Chevron down icon Chevron up icon
25. Having a Little Fun with Images with Pixel Manipulations Chevron down icon Chevron up icon
26. Saving an Image to SQL Server Chevron down icon Chevron up icon
27. Creating and Using an XML File Chevron down icon Chevron up icon
28. Creating XML Files with C# Chevron down icon Chevron up icon
29. Querying XML Documents with LINQ Chevron down icon Chevron up icon

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