How to display Windows.Form.MessageBox in ASP.NET web application?

I want to display my validation error messages in the MessageBox. I have Four TextBoxes and One Button control. When I click the Button Control, the TextBoxes without the text to be shown in the MessageBox. I have almost done this, but the problem is When I click the Button, the MessageBox is opened as a minimized window. So it is difficult for the end user to realize. I want to display the MessageBox to the user when button clicks.

Visual basic and Json.net Web request

Basically what im trying to do is make a program that list game information for league of legends.. using there API to extract data. how this works is you Search there username and it returns an integer linked to that account, you then use that integer to search for all of the information for that account, EG account level, wins, losses, etc.
I’ve run into a problem i can’t seem to figure out.. Please not that I’m very new to Json.net so have little experience about working with it.. Below is how the search for the user ID is found, The First section is the Username Minus Any spaces in the name the next is the ID which is the information i require.