C＃WebClient下载0字节的文件

Question

I tried to download a file from a URL using Webclient, but the downloaded files can't be opened and their size is 0 bytes,

could you please help me figure out what is the problem

below is the code i'm using :

using (WebClient client = new WebClient())
{
client.DownloadFile("https://anticipa-pre.crm4.dynamics.com/Activities/Attachment/download.aspx?AttachmentType=5&IsNotesTabAttachment=1&AttachmentId=dba4e278-2110-e911-8140-5065f38ada91&CRMWRPCToken=tzNg2xRKEemBV1Bl84vUEa8EEKjO6%2fTiao%2b9Wa9pQd%2f2CmDOgnckhoaIGqzrXSp6&CRMWRPCTokenTimeStamp=636838278955012633", 
                        @"C:\Users\ayousbai\DNIs\dni7.jpg");
}

Answer 1

Use Fiddler, or your browser, to test the download. Then you might see the error response or login screen.

In Firefox, I was redirected to:

login.microsoftonline.com