使用Post圖片上傳至後端一些方法整理
1.使用HttpPostedFileBase類別
2.檢查圖片格式
3.根目錄(取得RequestUrl)(https://ithelp.ithome.com.tw/articles/10211054)

public ActionResult ReadBarcode(IEnumerable<HttpPostedFileBase> files)
{
    if (files.Count() > 1)
    {
        foreach (var file in files)
        {
            if (file != null)
            {
                var fileName = $"{Path.GetFileName(file.FileName)}";
                var path = Path.Combine(Server.MapPath($"~/File/TheOldSchoolArt"), fileName);
                //副檔名
                string ext = file.FileName.Split('.')[file.FileName.Split('.').Length - 1];

                file.SaveAs(path);
            }
        }
    }
    return View();
}


/// <summary>
/// 檢查上傳檔案是否為圖片格式
/// </summary>
/// <param name="fileName">完整檔案名稱</param>
/// <returns>True or False</returns>
public static bool CheckPhotoFormat(string fileName)
{
    bool flag = false;
    string fileExtension = Path.GetExtension(fileName).ToLower();
    string[] allowedExtensions = { ".jpg", ".jpeg", ".png", ".gif" };

    for (int i = 0; i < allowedExtensions.Length; i++)
    {
        if (allowedExtensions[i].ToString().Equals(fileExtension))
        {
            flag = true;
        }
    }

    return flag;
}

    /// <summary>
    /// 取得RequestUrl()
    /// </summary>
    /// <param name="fileName"></param>
    /// <returns></returns>
    public static string GetImageRequestAbsoluteUriPath(string fileName,string somePath)
    {
        var requestAbsoluteUri = $"{HttpContext.Current.Request.Url.Scheme}://{HttpContext.Current.Request.Url.Authority}{somePath}{fileName}";
        return requestAbsoluteUri;
    }