how to disable right click on webbrowser control in vb .net windows application

The easiest way to do this is to disable the context menu of the document contained in the WebBrowser control e.g.

WebBrowser1.IsWebBrowserContextMenuEnabled = False

You could do this in the WebBrowser_Navigated event (rather than the Form_Load event) so that it applies to every page you might navigate to.

If you want to do something else when the User right-clicks in the browser control you actually want to handle the right-click rather than ignore it.

You could do something like this (the name of the function is arbitrary)

Private Sub WebDocument_MouseDown(ByVal sender As System.Object, ByVal e As HtmlElementEventArgs)
    If (e.MouseButtonsPressed = MouseButtons.Right) Then
        'Do what you want to do here
    End If
End Sub

And add the handler as

RemoveHandler WebBrowser1.Document.MouseDown, New HtmlElementEventHandler(AddressOf WebDocument_MouseDown)
AddHandler WebBrowser1.Document.MouseDown, New HtmlElementEventHandler(AddressOf WebDocument_MouseDown)

Note that I remove it first (there is no exception thrown if it doesn't exist) to prevent the handler being added multiple times.

Also note that if you have added a URL at design time then you should not add the handler in the Form_Load event as the WebBrowser.Document object will not yet exist (and an exception will be thrown). The WebBrowser_Navigated event is an appropriate place for this code. You will also need to set the IsWebBrowserContextMenuEnabled property to stop the context menu popping up after your WebDocument_MouseDown event has been processed