为了实现你的要求，你可以尝试下面的代码：
服务项目：

public class SQLiteDbService
{
    private readonly YourMainDbContext _mainDbContext;
    
    public SQLiteDbService(YourMainDbContext mainDbContext)
    {
        _mainDbContext = mainDbContext;
    }
    
    public async Task<string> CreateAndPopulateSQLiteDb(string deviceId)
    {
        var sqliteConnectionString = $"Data Source={deviceId}.db";
        var options = new DbContextOptionsBuilder<YourSQLiteDbContext>()
            .UseSqlite(sqliteConnectionString)
            .Options;

        await using var sqliteDbContext = new YourSQLiteDbContext(options);
        await sqliteDbContext.Database.EnsureCreatedAsync();
        
        var deviceData = _mainDbContext.Devices
            .Where(d => d.DeviceId == deviceId)
            .Include(/* include related data as necessary */)
            .FirstOrDefault();
        
        if (deviceData == null) throw new Exception("Device not found");
        
        sqliteDbContext.Devices.Add(deviceData);
        await sqliteDbContext.SaveChangesAsync();
        
        return sqliteConnectionString;
    }
    
    public async Task DeleteSQLiteDbFile(string connectionString)
    {
        var dbFilePath = new SqliteConnectionStringBuilder(connectionString).DataSource;
        if (File.Exists(dbFilePath))
        {
            File.Delete(dbFilePath);
        }
    }
}

字符串
控制器：

[ApiController]
[Route("api/[controller]")]
public class DeviceController : ControllerBase
{
    private readonly SQLiteDbService _sqliteDbService;

    public DeviceController(SQLiteDbService sqliteDbService)
    {
        _sqliteDbService = sqliteDbService;
    }

    [HttpGet("getDeviceData/{deviceId}")]
    public async Task<IActionResult> GetDeviceData(string deviceId)
    {
        try
        {
            var sqliteConnectionString = await _sqliteDbService.CreateAndPopulateSQLiteDb(deviceId);
            
            var dbFilePath = new SqliteConnectionStringBuilder(sqliteConnectionString).DataSource;
            var dbFileBytes = await System.IO.File.ReadAllBytesAsync(dbFilePath);
            var fileResult = new FileContentResult(dbFileBytes, "application/octet-stream")
            {
                FileDownloadName = "demofile.db"
            };

            await _sqliteDbService.DeleteSQLiteDbFile(sqliteConnectionString);

            return fileResult;
        }
        catch (Exception ex)
        {
            return StatusCode(500, ex.Message);
        }
    }
}

型
Startup.cs:

public void ConfigureServices(IServiceCollection services)
{
    .......
    services.AddDbContext<YourMainDbContext>(options => options.UseSqlServer("connection string"));
    services.AddScoped<SQLiteDbService>();
}

型