When Response.Flush() implements downloading of server-side files, it will fail and the IE download box will not pop up normally. Through testing, it was discovered that there is a security setting issue in the browser, which can be solved by the following operations
When downloading server-side files through Response.Flush(), it will fail and the IE download box will not pop up normally. After testing, it is found that the following settings need to be made to solve the problem.
Enter [Tools]--->[Internet Options]--->[Security]--->[Trusted Sites]
Changing the automatic prompt for file downloads to enabled can solve the problem.
Of course, you have to add the website you visit to a trusted site.