How to play video in ASP.NET program in default folder.?

ASP.NET doesn't really very much care, what video you load, where you load it from or how it is displayed in the browser. In ASP.NET, all that you need to do is,

<video src="/path/to/video.mp4">
   Browser does not support HTML5 video tag.
</video>

This is the maximum you need, then the video would come from the background, wherever you have stored it... Doesn't matter at all.

Now as for your two queries,

Quote:

if i click one button open one folder for our local folder to show that folder all files in listview or gridview

That is your duty, before loading the video, you can append the path of the video, local or server based virtual path etc. That is all to be controlled and defined by you, you can set a variable in the path and ASP.NET will automatically use that path before loading the video, such as,

@{
   var path = "/path/to";
}

<video src="@path/video.mp4">
   Browser does not support HTML5 video tag.
</video>

Quote:

play default video player in asp.net.

ASP.NET does not have a media player (forget about that old Silverlight control etc, no one wants to use that anymore!) You can easily rely on the HTML5 support for video element, and it loads the browser default. That is the best possible UX available.

Have a look here, Displaying Video in an ASP.NET Web Pages (Razor) Site | Microsoft Docs[^]