Published June 14, 2023
C# New (How It Works For Developers)
The C# programming language has a keyword called new. It's instrumental in creating a new instance of a class, struct, or array. The new keyword helps developers to define, create, and manipulate objects in C#
The Basics Understanding new Keyword in C#
The new keyword is at the heart of object-oriented programming in C#. The operator creates an instance of a class or struct. When we create an object, we're essentially defining a new instance of a class.
Let's take a look at this basic example of creating a new instance of a public class:
public class NewAuthor
{
public string Name { get; set; }
}
class Program
{
static void Main(string[] args)
{
NewAuthor author = new NewAuthor();
author.Name = "John Doe";
Console.WriteLine(author.Name);
}
}
public class NewAuthor
{
public string Name { get; set; }
}
class Program
{
static void Main(string[] args)
{
NewAuthor author = new NewAuthor();
author.Name = "John Doe";
Console.WriteLine(author.Name);
}
}
Public Class NewAuthor
Public Property Name() As String
End Class
Friend Class Program
Shared Sub Main(ByVal args() As String)
Dim author As New NewAuthor()
author.Name = "John Doe"
Console.WriteLine(author.Name)
End Sub
End ClassIn this example, we created a new instance of the NewAuthor class and set a property, Name, for the object. The code inside the constructor defines the properties of the newly created instance. We then outputted the name to the console.
Object Initialization New Feature in C#
One of the new features in C# allows developers to streamline object initialization using the new keyword. This is done by using an object initializer, which is a form of syntactic sugar that makes the code more readable.
In this example, we use an object initializer to create an instance of NewAuthor:
NewAuthor author = new NewAuthor { Name = "John Doe" };
Console.WriteLine(author.Name);NewAuthor author = new NewAuthor { Name = "John Doe" };
Console.WriteLine(author.Name);Dim author As New NewAuthor With {.Name = "John Doe"}
Console.WriteLine(author.Name)Notice the curly braces after new NewAuthor? That's the object initializer. It allows you to set properties or fields at the time of object creation.
Arrays and the new Keyword
The new keyword also works with arrays. For instance, when creating an array of integers, we use the new int[] syntax. Here's an example:
int[] numbers = new int[] {1, 2, 3, 4, 5};int[] numbers = new int[] {1, 2, 3, 4, 5};Dim numbers() As Integer = {1, 2, 3, 4, 5}In this line of code, we've created an array of integers, then initialized it with the values inside the curly braces.
Local Function and Lambda Expressions
A local function is a method that is defined inside another method. This function can access variables from the outer method. As of C# 9.0, a new feature is the ability to use the new keyword to define local functions inside lambda expressions.
Here's a simple example:
Func square = x =>
{
int localFunction(int y) => y * y;
return localFunction(x);
};
Console.WriteLine(square(5)); // Output: 25Func square = x =>
{
int localFunction(int y) => y * y;
return localFunction(x);
};
Console.WriteLine(square(5)); // Output: 25Private square As Func = Function(x)
' int localFunction(int y)
' {
' Return y * y;
' }
Return localFunction(x)
End Function
Console.WriteLine(square(5)) ' Output: 25In this snippet, we define a local function inside a lambda expression.
Operator Overloading and new
C# allows you to define or override the behavior of operators for your classes or structs. This is called operator overloading. The new operator is one of these.
While you can't override the new operator itself (as it is responsible for memory allocation and that can't be changed), you can use the new keyword to hide an inherited member from the base class.
public class BaseClass
{
public void Write()
{
Console.WriteLine("This is the base class.");
}
}
public class DerivedClass : BaseClass
{
public new void Write()
{
Console.WriteLine("This is the derived class.");
}
}public class BaseClass
{
public void Write()
{
Console.WriteLine("This is the base class.");
}
}
public class DerivedClass : BaseClass
{
public new void Write()
{
Console.WriteLine("This is the derived class.");
}
}Public Class BaseClass
Public Sub Write()
Console.WriteLine("This is the base class.")
End Sub
End Class
Public Class DerivedClass
Inherits BaseClass
Public Shadows Sub Write()
Console.WriteLine("This is the derived class.")
End Sub
End ClassIn this snippet, the new keyword hides the Write method from BaseClass in DerivedClass.
Target Typed new Expression
In C# 9.0, a new feature called target-typed new expressions was introduced. It allows us to instantiate an object of a class, struct, or array type without explicitly specifying the target type.
NewAuthor author = new() { Name = "John Doe" };NewAuthor author = new() { Name = "John Doe" };Dim author As New NewAuthor() With {.Name = "John Doe"}In this example, we don't have to specify the type NewAuthor in the new expression. The compiler infers the type from the context.
Anonymous Types and new Keyword
Anonymous types provide a convenient way to encapsulate a set of read-only properties into a single object without having to explicitly define a type. The new keyword plays an essential role in creating these anonymous types.
var author = new { Name = "John Doe", Age = 30 };
Console.WriteLine(author.Name);var author = new { Name = "John Doe", Age = 30 };
Console.WriteLine(author.Name);Dim author = New With {
Key .Name = "John Doe",
Key .Age = 30
}
Console.WriteLine(author.Name)This example shows the creation of an anonymous type with two properties: Name and Age. The new keyword here helps to create this anonymous type.
Error Handling with new
The new keyword can also be used to throw a new instance of an error message or exception. It's useful when you want to provide additional context about an error.
throw new Exception("This is a new error message.");throw new Exception("This is a new error message.");Throw New Exception("This is a new error message.")This line of code generates a new exception with a specific error message.
The new Keyword and Delegates
Delegates in C# are a type of object that can hold a reference to a method. They're especially useful when you want to pass methods as parameters. Delegates can also be instantiated using the new keyword.
public delegate void DisplayMessage(string message);
class Program
{
static void Main(string[] args)
{
DisplayMessage dm = new DisplayMessage(ShowMessage);
dm("Hello, World!");
}
static void ShowMessage(string message)
{
Console.WriteLine(message);
}
}public delegate void DisplayMessage(string message);
class Program
{
static void Main(string[] args)
{
DisplayMessage dm = new DisplayMessage(ShowMessage);
dm("Hello, World!");
}
static void ShowMessage(string message)
{
Console.WriteLine(message);
}
}Public Delegate Sub DisplayMessage(ByVal message As String)
Friend Class Program
Shared Sub Main(ByVal args() As String)
Dim dm As New DisplayMessage(AddressOf ShowMessage)
dm("Hello, World!")
End Sub
Private Shared Sub ShowMessage(ByVal message As String)
Console.WriteLine(message)
End Sub
End ClassIn this example, we first define a delegate called DisplayMessage that takes a string text as a parameter. In the Main method, we create a new instance of the delegate, passing in the ShowMessage method as a parameter. We then call the delegate, passing in a string to display on the console.
Generics and the new Constraint
Generics in C# allow for the definition of classes, interfaces, and methods with placeholders for the type of data they store or manipulate. A new constraint in C#
public class Example where T : new()
{
public T CreateInstance()
{
return new T();
}
}public class Example where T : new()
{
public T CreateInstance()
{
return new T();
}
}Public Class Example where T : Shadows()
Public Function CreateInstance() As T
Return New T()
End Function
End ClassIn this example, the new keyword is used in conjunction with a type parameter to create a new instance of the specified type.
Using the new Keyword with IronPDF
IronPDF is a popular library for extracting, editing, and creating PDFs using HTML in .NET applications. C#'s new keyword plays a vital role while working with this library.
To start, you create a new instance of the PdfDocument or PdfRenderer classes, allowing you to perform a range of operations on your PDF documents. Here's a quick example:
using IronPdf;
IronPdf.PdfDocument pdf = new IronPdf.PdfDocument("c:\\dotnet.pdf"); using IronPdf;
IronPdf.PdfDocument pdf = new IronPdf.PdfDocument("c:\\dotnet.pdf"); Imports IronPdf
Private pdf As New IronPdf.PdfDocument("c:\dotnet.pdf")In this example, we use the new keyword to create an instance of PdfDocument. We then load an existing file into the document. This is just the beginning of what you can do with IronPDF.
Working with IronPDF, the new keyword becomes a powerful tool. It lets you define, create, and manipulate PDF documents in a .NET environment in a way that's intuitive and efficient.
Conclusion
Mastering the new keyword in C# opens up a world of programming possibilities, from defining classes, structs, and arrays, to handling errors and working with powerful libraries such as IronPDF. Remember that like any skill, it takes practice to become proficient in C#
It's worth noting that IronPDF offers a 30-day free trial, which is an excellent opportunity to explore its capabilities firsthand. Once you've seen the benefits it brings to your PDF manipulation tasks, you can purchase a license starting from $749. It's a worthwhile investment for any .NET developer looking to streamline their PDF-related work.
