abp/framework/src/Volo.Abp.VirtualFileSystem/Volo/Abp/VirtualFileSystem/Embedded/EmbeddedResourceFileInfo.cs

using System;
using System.IO;
using System.Reflection;
using Microsoft.Extensions.FileProviders;

namespace Volo.Abp.VirtualFileSystem.Embedded;

/// <summary>
/// Represents a file embedded in an assembly.
/// </summary>
public class EmbeddedResourceFileInfo : IFileInfo
{
    public bool Exists => true;

    public long Length {
        get {
            if (!_length.HasValue)
            {
                using (var stream = _assembly.GetManifestResourceStream(_resourcePath))
                {
                    _length = stream!.Length;
                }
            }

            return _length.Value;
        }
    }
    private long? _length;

    public string? PhysicalPath => null;

    public string VirtualPath { get; }

    public string Name { get; }

    /// <summary>
    /// The time, in UTC.
    /// </summary>
    public DateTimeOffset LastModified { get; }

    public bool IsDirectory => false;

    private readonly Assembly _assembly;
    private readonly string _resourcePath;

    public EmbeddedResourceFileInfo(
        Assembly assembly,
        string resourcePath,
        string virtualPath,
        string name,
        DateTimeOffset lastModified)
    {
        _assembly = assembly;
        _resourcePath = resourcePath;

        VirtualPath = virtualPath;
        Name = name;
        LastModified = lastModified;
    }

    /// <inheritdoc />
    public Stream CreateReadStream()
    {
        var stream = _assembly.GetManifestResourceStream(_resourcePath);

        if (!_length.HasValue && stream != null)
        {
            _length = stream.Length;
        }

        return stream!;
    }

    public override string ToString()
    {
        return $"[EmbeddedResourceFileInfo] {Name} ({this.VirtualPath})";
    }
}