InvalidOperationException: No file provider has been configured to process the supplied file.

现在有一个api, 提供图片的下载，如下代码，，调试出现

InvalidOperationException: No file provider has been configured to process the supplied file. 的错误。

var rootPath =  _hostingEnvironment.ContentRootPath;
var photoName= "photo.jpeg";
bitmap.Save($@"{rootPath}\{photoName}", ImageFormat.Jpeg); // 变量bitmap 为Bitmap实例

return File(rootPath, "image/jpeg", photoName);

经过查找可以这样写，如下代码，这样就返回解决了问题。

var rootPath =  _hostingEnvironment.ContentRootPath;
var photoName= "photo.jpeg";
bitmap.Save($@"{rootPath}\{photoName}", ImageFormat.Jpeg);
// 一种方式
var provider = new PhysicalFileProvider(rootPath); // 或者这样写  var provider = _hostingEnvironment.ContentRootFileProvider;
var fileInfo = provider.GetFileInfo(photoName);
var readStream = fileInfo.CreateReadStream();

// 另一种更直接的方式// var readStream = System.IO.File.ReadAllBytes($@"{rootPath}\{photoName}");

return File(readStream, "image/jpeg", photoName);

参考：https://docs.microsoft.com/en-us/aspnet/core/fundamentals/file-providers?view=aspnetcore-2.2

本随笔链接：https://www.cnblogs.com/OneManStep/p/11358658.html