电子邮件格式转换器为 .NET

Aspose.Email LowCode Converter 提供一个简化、高级别的 API,以便在最小代码复杂度的不同格式之间转换电子邮件.

电子邮件:LowCode

是的 Aspose.Email.LowCode namespace 包含旨在简化电子邮件格式转换操作的课程 Converter 类,提供静态方法在流行格式之间转换电子邮件信息,包括EML,MSG,HTML,MHT,和MhTML.

关键组件

  • Converter :电子邮件格式转型的静态转换方法
  • IOutputHandler :处理转换输出流的界面
  • FolderOutputHandler :基于文件夹的输出存储的内置实施

开始使用

安装

通过 NuGet Package Manager 安装 Aspose.Email 包:

Install-Package Aspose.Email

名称宣言 

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

核心转换方法

基因格式转换

是的 Convert 方法提供灵活的格式转换,具有明确的输出类型规格:

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

示例實施:

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

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

专门转换方法

转换器提供专门的方法,用于常见的交换场景:

转换为HTML格式 

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

转换为 MSG 格式 

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

转换为EML格式 

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

转换为MHTML/MHT格式 

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

EML/MSG 特殊转换

自动格式检测中 EML 和 MSG 格式:

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

出口经销商实施

使用 FolderOutputHandler

內建的 FolderOutputHandler 类自动将转换的文件存储到指定的目录:

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

使用例子:

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

定制输出经销商

实施的 IOutputHandler 定制输出处理的界面:

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);
    }
}

支持格式矩阵

入口格式输出格式方法
EMLHTML、MSG、MHTML 和 MHTConvertToHtml(), ConvertToMsg(), 等等.
MSGHTML、EML、MHTML 和 MHTConvertToHtml(), ConvertToEml(), 等等.
任何电子邮件格式用户规格Convert() 输出类型参数

先进实施模式

包装处理实施 

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);
    }
}

错误处理模式 

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 
        };
    }
}

记忆优化流处理 

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);
}

配置和定制

输出目录结构

当使用 FolderOutputHandler, 转换器保持原始文件结构:

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

定义名称策略

通过专门的输出经销商实施自定义文件名称:

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
}

绩效考虑

非同步操作

所有转换方法返回 Task 对象,可有效无同步处理:

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

资源管理

正确的流量排放对最佳性能至关重要:

// 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);

記憶體使用最佳化

对于大型电子邮件文件,请考虑流媒体方法:

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);
}

集成示例

ASP.NET 核心 Web API 集成 

[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 服务实施 

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

常见问题及解决方案

问题解决方案
FileNotFoundException查看输入文件路径和许可证
UnauthorizedAccessException查看输出目录 写许可证
OutOfMemoryException使用大文件的流通方法
InvalidOperationException为输入文件提供有效的电子邮件格式

Debugging 提示

允许详细登录解决问题:

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;
    }
}
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