MapPath() Extension Method in ASP.NET: Map Physical Paths with an HttpContext.

MapPath_Extensions.cs

//ORIGINAL CODE BY RICK STRAHL https://weblog.west-wind.com/posts/2023/Aug/15/Map-Physical-Paths-with-an-HttpContextMapPath-Extension-Method-in-ASPNET
public static class HttpContextExtensions
{
    static string WebRootPath { get; set; }
    static string ContentRootPath { get; set; }

    /// <summary>
    /// Maps a virtual or relative path to a physical path in a Web site,
    /// using the WebRootPath as the base path (ie. the `wwwroot` folder)
    /// </summary>
    /// <param name="context">HttpContext instance</param>
    /// <param name="relativePath">Site relative path using either `~` or `/` as root indicator</param>
    /// <param name="host">Optional - IHostingEnvironment instance. If not passed retrieved from RequestServices DI</param>
    /// <param name="basePath">Optional - Optional physical base path. By default host.WebRootPath</param>
    /// <param name="useAppBasePath">Optional - if true returns the launch folder rather than the wwwroot folder</param>
    /// <returns>physical path of the relative path</returns>
    public static string MapPath(this HttpContext context, 
        string relativePath = null, 
        IWebHostEnvironment host = null, 
        string basePath = null, 
        bool useAppBasePath = false)
    {
        if (string.IsNullOrEmpty(relativePath))
            relativePath = "/";

        // Ignore absolute paths
        if (relativePath.StartsWith("https://", StringComparison.OrdinalIgnoreCase) ||
            relativePath.StartsWith("http://", StringComparison.OrdinalIgnoreCase))
            return relativePath;

        if (string.IsNullOrEmpty(basePath))
        {
            if(string.IsNullOrEmpty(WebRootPath) || string.IsNullOrEmpty(ContentRootPath))
            {
                //In ASP.NET Core versions prior to 3.0, there was no IWebHostEnvironment. 
                //Instead you had to use IHostingEnvironment to access ContentRootPath and WebRootPath. 
                host ??= context.RequestServices.GetService(typeof(IWebHostEnvironment)) as IWebHostEnvironment;
                WebRootPath = host.WebRootPath;
                ContentRootPath = host.ContentRootPath;
            }
            basePath = (useAppBasePath ? ContentRootPath : WebRootPath).TrimEnd('/', '\\');
        }

        relativePath = relativePath.TrimStart('~', '/', '\\');

        string path = Path.Combine(basePath, relativePath);

        string slash = Path.DirectorySeparatorChar.ToString();
        return path
            .Replace("/", slash)
            .Replace("\\", slash)
            .Replace(slash + slash, slash);
    }
}