Email Format Converter til .NET

Aspose.Email LowCode Converter giver en forenklet, højt niveau API til konvertering af e-mails mellem forskellige formater med minimal kode kompleksitet. Denne udviklerguide dækker de vigtigste funktionaliteter, implementeringsmønstre og bedste praksis for at bruge konverteren i .NET-applikationer.

Læs også: Email.LowCode

Den Aspose.Email.LowCode namespace indeholder klasser, der er designet til at streamline e-mail format konvertering operationer Converter klasse, der tilbyder statiske metoder til at omdanne e-mails mellem populære formater herunder EML, MSG, HTML, MHT og MHTML.

Nøglekomponenter

Converter : Statiske konverteringsmetoder til e-mailformats transformation
IoutputHandler : Grænseflade til håndtering af konverterede outputstrømme
FolderOutputHandler : Built-in implementation for mapperbaseret output opbevaring

At blive begyndt

Installation

Installér Aspose.Email-pakken via NuGet Package Manager:

Install-Package Aspose.Email

Namespace erklæring

using Aspose.Email.LowCode;
using System.IO;
using System.Threading.Tasks;

Core konverteringsmetoder

Generisk format konvertering

Den Convert Metoden giver fleksibel format konvertering med eksplicit udgangstype specifikation:

public static Task Convert(Stream input, string nameWithExtension, IOutputHandler handler, string outputType)

Eksempler på gennemførelse:

using var inputStream = File.OpenRead("email.eml");
var outputHandler = new FolderOutputHandler(@"C:\ConvertedEmails");

await Converter.Convert(inputStream, "email.eml", outputHandler, "html");

Specialiserede konverteringsmetoder

Converteren giver dedikerede metoder til almindelige konverteringscenarier:

Konverter til HTML-format

await Converter.ConvertToHtml(inputStream, "email.eml", outputHandler);

Konverter til MSG format

await Converter.ConvertToMsg(inputStream, "email.eml", outputHandler);

Konverter til EML format

await Converter.ConvertToEml(inputStream, "email.msg", outputHandler);

Konverteringer til MHTML/MHT-formater

await Converter.ConvertToMhtml(inputStream, "email.eml", outputHandler);
await Converter.ConvertToMht(inputStream, "email.eml", outputHandler);

EML/MSG specifik konvertering

Automatisk formatdetektion mellem EML og MSG Formaterne er:

await Converter.ConvertEmlOrMsg(inputStream, "email.eml", outputHandler, "html");

Udgangshandler implementering

Brug af FolderOutputHandler

Den indbyggede FolderOutputHandler Klassen gemmer automatisk konverterede filer til et angivet katalog:

public class FolderOutputHandler : IOutputHandler
{
    public FolderOutputHandler(string path)
    public string Path { get; set; }
}

Brug af eksempler:

var outputHandler = new FolderOutputHandler(@"C:\OutputDirectory");

Tilpasset udgangshandler

Implementation af IOutputHandler Interface til custom output processing:

public class CustomOutputHandler : IOutputHandler
{
    public async Task AddOutputStream(string name, Func<Stream, Task> writeAction)
    {
        // Custom async implementation
        using var customStream = CreateCustomStream(name);
        await writeAction(customStream);
    }
    
    public void AddOutputStream(string name, Action<Stream> writeAction)
    {
        // Custom synchronous implementation
        using var customStream = CreateCustomStream(name);
        writeAction(customStream);
    }
}

Støttet format matrix

Indtastet format	Udgangsformater	Method
EML	HTML, MSG, MHTML og MHT	`ConvertToHtml()`, `ConvertToMsg()`, Det osv.
MSG	HTML, EML, MHTML og MHT	`ConvertToHtml()`, `ConvertToEml()`, Det osv.
Enhver e-mail format	Brugerspecifikationer	`Convert()` med udgangstype parameter

Avancerede gennemførelsesmønstre

Batch Processing gennemførelse

public class EmailBatchConverter
{
    private readonly IOutputHandler _outputHandler;
    
    public EmailBatchConverter(IOutputHandler outputHandler)
    {
        _outputHandler = outputHandler;
    }
    
    public async Task ConvertBatch(IEnumerable<string> emailFiles, string outputFormat)
    {
        var conversionTasks = emailFiles.Select(async file =>
        {
            using var stream = File.OpenRead(file);
            var fileName = Path.GetFileName(file);
            
            await Converter.Convert(stream, fileName, _outputHandler, outputFormat);
        });
        
        await Task.WhenAll(conversionTasks);
    }
}

Fejl håndtering mønster

public async Task<ConversionResult> SafeConvert(string inputFile, string outputFormat)
{
    try
    {
        using var inputStream = File.OpenRead(inputFile);
        var outputHandler = new FolderOutputHandler(@"C:\Output");
        var fileName = Path.GetFileName(inputFile);
        
        await Converter.Convert(inputStream, fileName, outputHandler, outputFormat);
        
        return new ConversionResult { Success = true };
    }
    catch (Exception ex)
    {
        return new ConversionResult 
        { 
            Success = false, 
            ErrorMessage = ex.Message 
        };
    }
}

Memory-optimeret strømbearbejdning

public async Task ConvertWithMemoryOptimization(string inputFile)
{
    using var inputStream = new FileStream(inputFile, FileMode.Open, FileAccess.Read, FileShare.Read, 4096, useAsync: true);
    var outputHandler = new FolderOutputHandler(@"C:\Output");
    
    await Converter.ConvertToHtml(inputStream, Path.GetFileName(inputFile), outputHandler);
}

Konfiguration og tilpasning

Udgangsdirektør struktur

Når man bruger FolderOutputHandler, Konverteren opretholder den oprindelige filstruktur:

var outputHandler = new FolderOutputHandler(@"C:\ConvertedEmails");
// Original: sample.eml → Output: C:\ConvertedEmails\sample.html

Tilpasset navnestrategi

Implementering af brugerdefineret filnavne gennem en specialiseret output handler:

public class TimestampOutputHandler : IOutputHandler
{
    private readonly string _basePath;
    
    public TimestampOutputHandler(string basePath)
    {
        _basePath = basePath;
    }
    
    public async Task AddOutputStream(string name, Func<Stream, Task> writeAction)
    {
        var timestamp = DateTime.Now.ToString("yyyyMMdd_HHmmss");
        var newName = $"{timestamp}_{name}";
        var filePath = Path.Combine(_basePath, newName);
        
        using var fileStream = File.Create(filePath);
        await writeAction(fileStream);
    }
    
    // Synchronous implementation omitted for brevity
}

Performance overvejelser

Asynkron operationer

Alle konverteringsmetoder vender tilbage Task objekter, der muliggør effektiv asynkron behandling:

public async Task ProcessMultipleEmailsAsync()
{
    var tasks = new[]
    {
        ConvertEmailAsync("email1.eml"),
        ConvertEmailAsync("email2.msg"),
        ConvertEmailAsync("email3.eml")
    };
    
    await Task.WhenAll(tasks);
}

Resource Management

Korrekt strømforsyning er afgørende for optimal ydeevne:

// Correct pattern
using (var inputStream = File.OpenRead("email.eml"))
{
    await Converter.ConvertToHtml(inputStream, "email.eml", outputHandler);
}

// Alternative using statement
using var inputStream = File.OpenRead("email.eml");
await Converter.ConvertToHtml(inputStream, "email.eml", outputHandler);

Optimering af hukommelse

For store e-mail filer, overveje streaming tilgange:

public async Task ConvertLargeEmail(string inputPath)
{
    const int bufferSize = 65536; // 64KB buffer
    
    using var inputStream = new FileStream(inputPath, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize, true);
    var outputHandler = new FolderOutputHandler(@"C:\Output");
    
    await Converter.ConvertToHtml(inputStream, Path.GetFileName(inputPath), outputHandler);
}

Integration eksempler

ASP.NET Core Web API integration

[ApiController]
[Route("api/[controller]")]
public class EmailConverterController : ControllerBase
{
    [HttpPost("convert")]
    public async Task<IActionResult> ConvertEmail(IFormFile emailFile, [FromQuery] string format = "html")
    {
        if (emailFile == null || emailFile.Length == 0)
            return BadRequest("No file provided");
        
        try
        {
            using var inputStream = emailFile.OpenReadStream();
            var outputHandler = new MemoryOutputHandler();
            
            await Converter.Convert(inputStream, emailFile.FileName, outputHandler, format);
            
            return File(outputHandler.GetContent(), GetContentType(format), $"converted.{format}");
        }
        catch (Exception ex)
        {
            return StatusCode(500, $"Conversion failed: {ex.Message}");
        }
    }
    
    private string GetContentType(string format) => format.ToLower() switch
    {
        "html" => "text/html",
        "mhtml" => "message/rfc822",
        "eml" => "message/rfc822",
        _ => "application/octet-stream"
    };
}

Windows Service gennemførelse

public class EmailConverterService : BackgroundService
{
    private readonly string _watchFolder;
    private readonly string _outputFolder;
    
    public EmailConverterService(IConfiguration config)
    {
        _watchFolder = config["EmailConverter:WatchFolder"];
        _outputFolder = config["EmailConverter:OutputFolder"];
    }
    
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var watcher = new FileSystemWatcher(_watchFolder, "*.eml");
        watcher.Created += async (sender, e) => await ProcessEmailFile(e.FullPath);
        watcher.EnableRaisingEvents = true;
        
        while (!stoppingToken.IsCancellationRequested)
        {
            await Task.Delay(1000, stoppingToken);
        }
    }
    
    private async Task ProcessEmailFile(string filePath)
    {
        using var inputStream = File.OpenRead(filePath);
        var outputHandler = new FolderOutputHandler(_outputFolder);
        
        await Converter.ConvertToHtml(inputStream, Path.GetFileName(filePath), outputHandler);
    }
}

Troubleshooting

fælles problemer og løsninger

Spørgsmål	Løsning
`FileNotFoundException`	Kontroller indtastningsfilen vej og tilladelser
`UnauthorizedAccessException`	Check output directory skrive tilladelser
`OutOfMemoryException`	Brug streamingmetode til store filer
`InvalidOperationException`	Sikre gyldig e-mail format for input filer

Debugging tips

Det giver mulighed for detaljeret logging til problemløsning:

public async Task ConvertWithLogging(string inputFile)
{
    var logger = LoggerFactory.Create(builder => builder.AddConsole()).CreateLogger<EmailConverter>();
    
    try
    {
        logger.LogInformation($"Starting conversion of {inputFile}");
        
        using var inputStream = File.OpenRead(inputFile);
        var outputHandler = new FolderOutputHandler(@"C:\Output");
        
        await Converter.ConvertToHtml(inputStream, Path.GetFileName(inputFile), outputHandler);
        
        logger.LogInformation($"Successfully converted {inputFile}");
    }
    catch (Exception ex)
    {
        logger.LogError(ex, $"Failed to convert {inputFile}");
        throw;
    }
}