C# 扩展方法（开发者如何使用）

public static class StringExtensions
{
    // This extension method counts the number of words in a string.
    public static int WordCount(this string input)
    {
        // Split the string by whitespace characters and return the length of the resulting array.
        return input.Split(new[] { ' ', '\t', '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries).Length;
    }
}

Imports Microsoft.VisualBasic

Public Module StringExtensions
	' This extension method counts the number of words in a string.
	<System.Runtime.CompilerServices.Extension> _
	Public Function WordCount(ByVal input As String) As Integer
		' Split the string by whitespace characters and return the length of the resulting array.
		Return input.Split( { " "c, ControlChars.Tab, ControlChars.Cr, ControlChars.Lf }, StringSplitOptions.RemoveEmptyEntries).Length
	End Function
End Module

string text = "Extension methods are awesome!";
int wordCount = text.WordCount();
Console.WriteLine($"The text has {wordCount} words."); // Output: The text has 4 words.

Dim text As String = "Extension methods are awesome!"
Dim wordCount As Integer = text.WordCount()
Console.WriteLine($"The text has {wordCount} words.") ' Output: The text has 4 words.

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

public static class EnumerableExtensions
{
    // This extension method calculates the median of a collection of integers.
    public static double Median(this IEnumerable<int> source)
    {
        // Sort the collection and convert it to an array.
        int[] sorted = source.OrderBy(x => x).ToArray();
        int count = sorted.Length;

        if (count == 0)
        {
            throw new InvalidOperationException("The collection is empty.");
        }

        // If the count is even, return the average of the two middle elements.
        if (count % 2 == 0)
        {
            return (sorted[count / 2 - 1] + sorted[count / 2]) / 2.0;
        }
        else
        {
            // Otherwise, return the middle element.
            return sorted[count / 2];
        }
    }
}

Imports System
Imports System.Collections.Generic
Imports System.Linq

Public Module EnumerableExtensions
	' This extension method calculates the median of a collection of integers.
	<System.Runtime.CompilerServices.Extension> _
	Public Function Median(ByVal source As IEnumerable(Of Integer)) As Double
		' Sort the collection and convert it to an array.
		Dim sorted() As Integer = source.OrderBy(Function(x) x).ToArray()
		Dim count As Integer = sorted.Length

		If count = 0 Then
			Throw New InvalidOperationException("The collection is empty.")
		End If

		' If the count is even, return the average of the two middle elements.
		If count Mod 2 = 0 Then
			Return (sorted(count \ 2 - 1) + sorted(count \ 2)) / 2.0
		Else
			' Otherwise, return the middle element.
			Return sorted(count \ 2)
		End If
	End Function
End Module

int[] numbers = { 5, 3, 9, 1, 4 };
double median = numbers.Median();
Console.WriteLine($"The median value is {median}."); // Output: The median value is 4.

Dim numbers() As Integer = { 5, 3, 9, 1, 4 }
Dim median As Double = numbers.Median()
Console.WriteLine($"The median value is {median}.") ' Output: The median value is 4.

public static class DateTimeExtensions
{
    // This extension method calculates the start of the week for a given date.
    public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek = DayOfWeek.Monday)
    {
        // Calculate the difference in days between the current day and the start of the week.
        int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;
        // Subtract the difference to get the start of the week.
        return dt.AddDays(-1 * diff).Date;
    }
}

Public Module DateTimeExtensions
	' This extension method calculates the start of the week for a given date.
'INSTANT VB NOTE: The parameter startOfWeek was renamed since Visual Basic will not allow parameters with the same name as their enclosing function or property:
	<System.Runtime.CompilerServices.Extension> _
	Public Function StartOfWeek(ByVal dt As DateTime, Optional ByVal startOfWeek_Conflict As DayOfWeek = DayOfWeek.Monday) As DateTime
		' Calculate the difference in days between the current day and the start of the week.
		Dim diff As Integer = (7 + (dt.DayOfWeek - startOfWeek_Conflict)) Mod 7
		' Subtract the difference to get the start of the week.
		Return dt.AddDays(-1 * diff).Date
	End Function
End Module

DateTime today = DateTime.Today;
DateTime startOfWeek = today.StartOfWeek();
Console.WriteLine($"The start of the week is {startOfWeek.ToShortDateString()}.");
// Output will depend on the current date, e.g. The start of the week is 17/06/2024.

Dim today As DateTime = DateTime.Today
Dim startOfWeek As DateTime = today.StartOfWeek()
Console.WriteLine($"The start of the week is {startOfWeek.ToShortDateString()}.")
' Output will depend on the current date, e.g. The start of the week is 17/06/2024.

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();
        var PDF = renderer.RenderHtmlAsPdf("Hello, World!");
        PDF.SaveAs("HelloWorld.PDF");
    }
}

Imports IronPdf

Friend Class Program
	Shared Sub Main(ByVal args() As String)
		Dim renderer = New ChromePdfRenderer()
		Dim PDF = renderer.RenderHtmlAsPdf("Hello, World!")
		PDF.SaveAs("HelloWorld.PDF")
	End Sub
End Class

using IronPdf;

public static class StringExtensions
{
    // This extension method converts a string containing HTML to a PDF and saves it.
    public static void SaveAsPdf(this string htmlContent, string filePath)
    {
        var renderer = new ChromePdfRenderer();
        var PDF = renderer.RenderHtmlAsPdf(htmlContent);
        PDF.SaveAs(filePath);
    }
}

Imports IronPdf

Public Module StringExtensions
	' This extension method converts a string containing HTML to a PDF and saves it.
	<System.Runtime.CompilerServices.Extension> _
	Public Sub SaveAsPdf(ByVal htmlContent As String, ByVal filePath As String)
		Dim renderer = New ChromePdfRenderer()
		Dim PDF = renderer.RenderHtmlAsPdf(htmlContent)
		PDF.SaveAs(filePath)
	End Sub
End Module

string html = "<h1>Extension Methods and IronPDF</h1><p>Generating PDFs has never been easier!</p>";
html.SaveAsPdf("ExtensionMethodsAndIronPDF.PDF");

Dim html As String = "<h1>Extension Methods and IronPDF</h1><p>Generating PDFs has never been easier!</p>"
html.SaveAsPdf("ExtensionMethodsAndIronPDF.PDF")

using IronPdf;

public static class UriExtensions
{
    // This extension method converts a web URL to a PDF and saves it.
    public static void SaveAsPdf(this Uri url, string filePath)
    {
        var renderer = new ChromePdfRenderer();
        var PDF = renderer.RenderUrlAsPdf(url.AbsoluteUri);
        PDF.SaveAs(filePath);
    }
}

Imports IronPdf

Public Module UriExtensions
	' This extension method converts a web URL to a PDF and saves it.
	<System.Runtime.CompilerServices.Extension> _
	Public Sub SaveAsPdf(ByVal url As Uri, ByVal filePath As String)
		Dim renderer = New ChromePdfRenderer()
		Dim PDF = renderer.RenderUrlAsPdf(url.AbsoluteUri)
		PDF.SaveAs(filePath)
	End Sub
End Module

Uri url = new Uri("https://www.ironpdf.com/");
url.SaveAsPdf("UrlToPdf.PDF");

Dim url As New Uri("https://www.ironpdf.com/")
url.SaveAsPdf("UrlToPdf.PDF")