The following sample code demonstrates how to change the value of a particular node.

using DotNetBrowser; 
using DotNetBrowser.DOM; 
using DotNetBrowser.Events; 

//... 
Browser browser = BrowserFactory.Create(); 
browser.FinishLoadingFrameEvent += delegate(object sender, FinishLoadingEventArgs e) 
{
    if (e.IsMainFrame)
    {
        DOMDocument document = e.Browser.GetDocument();
        DOMElement button = document.GetElementById("button-id");
        button.Children[0].NodeValue = "New Button Name"; 
    } 
}; 

browser.LoadHTML("<html><body><button id='button-id'>Button</button></body></html>");