You can find documentation of this configuration element at iis.net/ConfigReference. This is the equivalent of:
Opening Internet Information Services (IIS Manager)
Navigating through the tree-view on the left until you reach the virtual directory you wish to modify
Selecting the appropriate virtual directory so that the title of the right-hand pane becomes the name of said virtual directory.
Choosing "Compression" under "IIS" in the right-hand pane
Ticking both options and choosing "Apply" under "Actions" on the far right.
Note: (As pointed out in the comments) You need to ensure that Http Dynamic Compression is installed otherwise setting doDynamicCompression="true" will not have any effect. The quickest way to do this is:
Start > Type optionalfeatures (this is the quickest way to get to the "Turn Windows Features on or off" window)
Navigate to Internet Information Services > World Wide Web Services > Performance Features in the "Windows Features" treeview
Ensure "Dynamic Content Compression" is ticked
Click "Ok" and wait whilst Windows installs the component
You could do this in code if you rather do that. I would make a basecontroller which every control inherits from and decorate it with this attribute below.
public class CompressAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
var encodingsAccepted = filterContext.HttpContext.Request.Headers["Accept-Encoding"];
if (string.IsNullOrEmpty(encodingsAccepted)) return;
encodingsAccepted = encodingsAccepted.ToLowerInvariant();
var response = filterContext.HttpContext.Response;
if (encodingsAccepted.Contains("deflate"))
{
response.AppendHeader("Content-encoding", "deflate");
response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
}
else if (encodingsAccepted.Contains("gzip"))
{
response.AppendHeader("Content-encoding", "gzip");
response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
}
}
}