实现外部存储文件强制下载：Content-Disposition 的关键作用

Content-Disposition: attachment; filename="your_file_name.ext"

using Azure.Storage.Blobs;
using Azure.Storage.Sas;
using System;

public class BlobDownloadHelper
{
    private readonly BlobServiceClient _blobServiceClient;

    public BlobDownloadHelper(string connectionString)
    {
        _blobServiceClient = new BlobServiceClient(connectionString);
    }

    /// <summary>
    /// 生成一个带有Content-Disposition的Blob下载SAS URI
    /// </summary>
    /// <param name="containerName">Blob容器名称</param>
    /// <param name="blobName">Blob名称</param>
    /// <param name="fileNameForDownload">下载时显示的文件名</param>
    /// <param name="sasExpiryMinutes">SAS URI的有效期（分钟）</param>
    /// <returns>带有Content-Disposition的SAS URI</returns>
    public Uri GenerateDownloadSasUri(string containerName, string blobName, string fileNameForDownload, int sasExpiryMinutes = 60)
    {
        // 获取Blob客户端
        BlobClient blobClient = _blobServiceClient.GetBlobContainerClient(containerName).GetBlobClient(blobName);

        // 检查Blob是否存在
        if (!blobClient.Exists())
        {
            throw new InvalidOperationException($"Blob '{blobName}' in container '{containerName}' does not exist.");
        }

        // 创建BlobSasBuilder对象
        BlobSasBuilder sasBuilder = new BlobSasBuilder()
        {
            BlobContainerName = containerName,
            BlobName = blobName,
            Resource = "b", // "b" for blob, "c" for container
            StartsOn = DateTimeOffset.UtcNow,
            ExpiresOn = DateTimeOffset.UtcNow.AddMinutes(sasExpiryMinutes)
        };

        // 设置SAS权限，允许读取
        sasBuilder.SetPermissions(BlobSasPermissions.Read);

        // 关键步骤：设置Content-Disposition，强制浏览器下载
        // "attachment" 指示浏览器下载文件，而不是在浏览器中显示
        // filename 参数指定下载时文件的默认名称
        sasBuilder.ContentDisposition = $"attachment; filename=\"{fileNameForDownload}\"";

        // 生成SAS URI
        Uri sasUri = blobClient.GenerateSasUri(sasBuilder);

        return sasUri;
    }

    public static void Main(string[] args)
    {
        string connectionString = "DefaultEndpointsProtocol=https;AccountName=your_account_name;AccountKey=your_account_key;EndpointSuffix=core.windows.net";
        string containerName = "my-files";
        string blobName = "document.pdf";
        string downloadFileName = "MyReport.pdf";

        try
        {
            BlobDownloadHelper helper = new BlobDownloadHelper(connectionString);
            Uri downloadUri = helper.GenerateDownloadSasUri(containerName, blobName, downloadFileName);
            Console.WriteLine($"Generated Download URI: {downloadUri}");
            // 这个URI现在可以在前端的<a>标签中使用，确保触发下载
            // <a href="{downloadUri}" download="{downloadFileName}">下载文件</a>
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
        }
    }
}