C# Wahr falsch (Wie es für Entwickler funktioniert)

What is a Boolean?

A boolean is a data type that has only two values – true and false. This binary nature can be thought of as an on-off switch. In C#, the keywords to represent these values are true and false, respectively.

For example, consider the light switch in your room. It can either be ON (true) or OFF (false). The same principle applies here.

Declaring a Bool Variable in C#

In C#, you can declare a bool variable as shown in the below example.

bool isLightOn = true;

bool isLightOn = true;

Dim isLightOn As Boolean = True

Here, isLightOn is a bool variable that has been assigned the value true.

The Role of Boolean Operators

In C#, true and false are not just values. They are operators that play a significant role in boolean expressions and boolean logic. These determine the outcome of conditions and can be used in various constructs, especially the if statements.

Logical Operators with True and False

C# offers a range of logical operators that work alongside true and false to assess and manipulate boolean expressions.

AND (&&): Returns true if both expressions are true.

bool result = true && false;  // result is false

bool result = true && false;  // result is false

Dim result As Boolean = True AndAlso False ' result is false

OR (||): Returns true if at least one of the expressions is true.

bool result = true || false;  // result is true

bool result = true || false;  // result is true

Dim result As Boolean = True OrElse False ' result is true

NOT (!): Inverts the value of an expression.

bool result = !true;  // result is false

bool result = !true;  // result is false

Dim result As Boolean = Not True ' result is false

Overloading True and False Operators

In C#, you can define custom behavior for true and false operators in user-defined types by overloading them. This means you can dictate how your custom objects evaluate to true or false.

For example, consider a class that represents a light bulb:

public class LightBulb
{
    public int Brightness { get; set; }

    public static bool operator true(LightBulb bulb)
    {
        return bulb.Brightness > 50;
    }

    public static bool operator false(LightBulb bulb)
    {
        return bulb.Brightness <= 50;
    }
}

public class LightBulb
{
    public int Brightness { get; set; }

    public static bool operator true(LightBulb bulb)
    {
        return bulb.Brightness > 50;
    }

    public static bool operator false(LightBulb bulb)
    {
        return bulb.Brightness <= 50;
    }
}

Public Class LightBulb
	Public Property Brightness() As Integer

	Public Shared Operator IsTrue(ByVal bulb As LightBulb) As Boolean
		Return bulb.Brightness > 50
	End Operator

	Public Shared Operator IsFalse(ByVal bulb As LightBulb) As Boolean
		Return bulb.Brightness <= 50
	End Operator
End Class

With the above code, a LightBulb object with a Brightness value greater than 50 evaluates to true, otherwise, it evaluates to false.

Conditional Operators

C# also provides conditional operators that return a bool value.

Equality (==): Checks if two values are equal.

bool result = (5 == 5);  // result is true

bool result = (5 == 5);  // result is true

Dim result As Boolean = (5 = 5) ' result is true

Inequality (!=): Checks if two values are not equal.

bool result = (5 != 5);  // result is false

bool result = (5 != 5);  // result is false

Dim result As Boolean = (5 <> 5) ' result is false

Greater than (>), Less than (<), Greater than or equal to (>=), and Less than or equal to (<=): Used to compare numeric (int) or other comparable types.

bool isGreater = (10 > 5);  // isGreater is true

bool isGreater = (10 > 5);  // isGreater is true

Dim isGreater As Boolean = (10 > 5) ' isGreater is true

What is a Boolean Expression?

A boolean expression is a statement that evaluates to either true or false. For instance:

int a = 5;
int b = 10;
bool result = a > b;  // This will evaluate to false

int a = 5;
int b = 10;
bool result = a > b;  // This will evaluate to false

Dim a As Integer = 5
Dim b As Integer = 10
Dim result As Boolean = a > b ' This will evaluate to false

Here, a > b is a boolean expression. The expression evaluates to false because 5 is not greater than 10.

Using Boolean Expressions with the if Statement

The primary use of boolean expressions in C# is within the if statement. The code inside the if statement runs only if the boolean expression is true.

if (isLightOn)
{
    Console.WriteLine("The light is on!");
}

if (isLightOn)
{
    Console.WriteLine("The light is on!");
}

If isLightOn Then
	Console.WriteLine("The light is on!")
End If

In the above snippet, the code inside the if statement will run because isLightOn is true.

Introducing Nullable Value Types

Sometimes, you may encounter situations where a variable might not have a value. For instance, if you're getting data from an external source, a boolean field might either be true, false, or unknown (i.e., no value).

C# introduces nullable value types for such scenarios. For Booleans, this is represented as bool?, which stands for nullable bool operator.

Declaring and Using Nullable Booleans

A nullable bool can take three values: true, false, or null. Here's how you can declare a nullable boolean:

bool? isDataAvailable = null;

bool? isDataAvailable = null;

Dim isDataAvailable? As Boolean = Nothing

Now, isDataAvailable doesn't have any of the two values we discussed earlier. Instead, it's null, indicating the absence of a value.

Checking Nullable Booleans

You might be wondering how to check the value of a nullable bool. Here's how you can do it:

if (isDataAvailable == true)
{
    Console.WriteLine("Data is available.");
}
else if (isDataAvailable == false)
{
    Console.WriteLine("Data is not available.");
}
else
{
    Console.WriteLine("Data availability is unknown.");
}

if (isDataAvailable == true)
{
    Console.WriteLine("Data is available.");
}
else if (isDataAvailable == false)
{
    Console.WriteLine("Data is not available.");
}
else
{
    Console.WriteLine("Data availability is unknown.");
}

If isDataAvailable = True Then
	Console.WriteLine("Data is available.")
ElseIf isDataAvailable = False Then
	Console.WriteLine("Data is not available.")
Else
	Console.WriteLine("Data availability is unknown.")
End If

Notice how we compare the nullable bool with both true and false operators. If neither is a match, it means the value is null.

IronPDF

Explore IronPDF Features - IronPDF is a robust tool for creating, editing, and extracting content from PDF documents. Think of scenarios where you've generated a report and need to verify if the generation was successful. Using boolean checks, you can ensure the integrity of your PDFs. An operation might return true if the PDF meets certain conditions or false otherwise, demonstrating the intertwined nature of boolean logic with PDF operations.

IronPDF’s primary strength is in converting HTML to PDF documents, ensuring that the original layouts and styles are preserved. It’s particularly useful for generating PDFs from web-based content like reports, invoices, and documentation. It works with HTML files, URLs, and HTML strings to create PDFs.

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

Imports IronPdf

Friend Class Program
	Shared Sub Main(ByVal args() As String)
		Dim renderer = New ChromePdfRenderer()

		' 1. Convert HTML String to PDF
		Dim htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>"
		Dim pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent)
		pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf")

		' 2. Convert HTML File to PDF
		Dim htmlFilePath = "path_to_your_html_file.html" ' Specify the path to your HTML file
		Dim pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath)
		pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf")

		' 3. Convert URL to PDF
		Dim url = "http://ironpdf.com" ' Specify the URL
		Dim pdfFromUrl = renderer.RenderUrlAsPdf(url)
		pdfFromUrl.SaveAs("URLToPDF.pdf")
	End Sub
End Class

IronXL

Discover IronXL for Excel Management - IronXL offers capabilities to work with Excel sheets, be it reading, writing, or manipulating data. When working with vast datasets in Excel, boolean values often become indispensable. For instance, validating whether data meets specific criteria or checking the success of a data import operation typically results in a true or false outcome. Thus, IronXL and boolean values often go hand-in-hand in data validation and operations.

IronOCR

Learn More About IronOCR - IronOCR is an Optical Character Recognition tool, that allows developers to extract text from images and documents. In the context of OCR, boolean values play a pivotal role in verifying the success of text extraction. For example, after processing an image, the software might indicate (true or false) whether the extraction was successful or if the scanned content matches the expected values.

IronBarcode

Explore IronBarcode Capabilities - Last, but certainly not least, IronBarcode provides functionality for generating and scanning barcodes. As with other tools in the Iron Suite, boolean logic is essential. After scanning a barcode or QR code, a boolean check can swiftly tell you if the barcode was recognized or if the generated barcode adheres to specific standards.