c# - HttpFileCollection 中的无效转换异常

Question

我在下面有一个扩展方法，但是当我运行它时，foreach 给我 InvalidCastException 并且它说 *

Unable to cast object of type 'System.String' to type 'System.Web.HttpPostedFile'.

代码:

public static List<Attachment> GetFiles(this HttpFileCollection collection) {
            if (collection.Count > 0) {
                List<Attachment> items = new List<Attachment>();
                foreach (HttpPostedFile _file in collection) {
                    if (_file.ContentLength > 0)
                        items.Add(new Attachment()
                        {
                            ContentType = _file.ContentType,
                            Name = _file.FileName.LastIndexOf('\\') > 0 ? _file.FileName.Substring(_file.FileName.LastIndexOf('\\') + 1) : _file.FileName,
                            Size = _file.ContentLength / 1024,
                            FileContent = new Binary(new BinaryReader(_file.InputStream).ReadBytes((int)_file.InputStream.Length))
                        });

                    else
                        continue;
                }
                return items;
            } else
                return null;
        }

提前致谢。

MSDN 说:

Clients encode files and transmit them in the content body using multipart MIME format with an HTTP Content-Type header of multipart/form-data. ASP.NET extracts the encoded file(s) from the content body into individual members of an HttpFileCollection. Methods and properties of the HttpPostedFile class provide access to the contents and properties of each file.

Answer 1

如果您查看此页面上的代码示例，它显示了您应该如何枚举集合，实际上，当您尝试按原样枚举时，您得到的是一个字符串。

http://msdn.microsoft.com/en-us/library/system.web.httpfilecollection.aspx