C# Concurrentdictionary（它是如何運作的開發者用途）

var filePath = pdfCache.GetOrAdd(userId, id => GeneratePdfForUser(id));

Dim filePath = pdfCache.GetOrAdd(userId, Function(id) GeneratePdfForUser(id))

pdfCache.AddOrUpdate(userId,
    id => GeneratePdfForUser(id),
    (id, existingValue) => UpdatePdfForUser(id, existingValue));

pdfCache.AddOrUpdate(userId, Function(id) GeneratePdfForUser(id), Function(id, existingValue) UpdatePdfForUser(id, existingValue))

bool added = pdfCache.TryAdd(userId, pdfBytes);
if (!added)
{
    Console.WriteLine("PDF already cached.");
}

Dim added As Boolean = pdfCache.TryAdd(userId, pdfBytes)
If Not added Then
	Console.WriteLine("PDF already cached.")
End If

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;
using IronPdf;
public class Program
{
    static ConcurrentDictionary<string, byte[]> pdfReports =
        new ConcurrentDictionary<string, byte[]>();
    static void Main(string[] args)
    {
        // Simulated user list with HTML content
        var users = new List<User>
        {
            new User { Id = "user1", HtmlContent = "<h1>Report for User 1</h1>" },
            new User { Id = "user2", HtmlContent = "<h1>Report for User 2</h1>" },
            new User { Id = "user3", HtmlContent = "<h1>Report for User 3</h1>" }
        };
        // Generate PDFs concurrently
        var renderer = new ChromePdfRenderer();
        Parallel.ForEach(users, user =>
        {
            var pdf = pdfReports.GetOrAdd(user.Id, id =>
            {
                var pdfDoc = renderer.RenderHtmlAsPdf(user.HtmlContent);
                return pdfDoc.BinaryData;
            });
            SaveToFile(pdf, $"{user.Id}.pdf");
        });
        Console.WriteLine("PDF generation complete.");
    }
    // Utility method to write PDF binary data to file
    static void SaveToFile(byte[] pdfBytes, string filePath)
    {
        File.WriteAllBytes(filePath, pdfBytes);
        Console.WriteLine($"Saved: {filePath}");
    }
}
// Simple user class with ID and HTML content
public class User
{
    public string Id { get; set; }
    public string HtmlContent { get; set; }
}

Imports System
Imports System.Collections.Concurrent
Imports System.Collections.Generic
Imports System.IO
Imports System.Threading.Tasks
Imports IronPdf
Public Class Program
	Private Shared pdfReports As New ConcurrentDictionary(Of String, Byte())()
	Shared Sub Main(ByVal args() As String)
		' Simulated user list with HTML content
		Dim users = New List(Of User) From {
			New User With {
				.Id = "user1",
				.HtmlContent = "<h1>Report for User 1</h1>"
			},
			New User With {
				.Id = "user2",
				.HtmlContent = "<h1>Report for User 2</h1>"
			},
			New User With {
				.Id = "user3",
				.HtmlContent = "<h1>Report for User 3</h1>"
			}
		}
		' Generate PDFs concurrently
		Dim renderer = New ChromePdfRenderer()
		Parallel.ForEach(users, Sub(user)
			Dim pdf = pdfReports.GetOrAdd(user.Id, Function(id)
				Dim pdfDoc = renderer.RenderHtmlAsPdf(user.HtmlContent)
				Return pdfDoc.BinaryData
			End Function)
			SaveToFile(pdf, $"{user.Id}.pdf")
		End Sub)
		Console.WriteLine("PDF generation complete.")
	End Sub
	' Utility method to write PDF binary data to file
	Private Shared Sub SaveToFile(ByVal pdfBytes() As Byte, ByVal filePath As String)
		File.WriteAllBytes(filePath, pdfBytes)
		Console.WriteLine($"Saved: {filePath}")
	End Sub
End Class
' Simple user class with ID and HTML content
Public Class User
	Public Property Id() As String
	Public Property HtmlContent() As String
End Class