With DotNetBrowser you can zoom the web page content using the Browser.ZoomLevelproperty and Browser.ZoomIn()Browser.ZoomOut(), Browser.ZoomReset() methods. 


Please note that zoom level can be applied only to the completely loaded web page. You need to wait until the web page is loaded completely and only then you can zoom it:

C#

browser.FinishLoadingFrameEvent += delegate(object sender, FinishLoadingEventArgs e)
{
  // Wait until main document of the web page is loaded completely.
  if (e.IsMainFrame)
  {
    e.Browser.ZoomLevel = 2.0;
  }
};

VB.NET

AddHandler browser.FinishLoadingFrameEvent,
    sub(sender As Object, e As FinishLoadingEventArgs)
        ' Wait until main document of the web page is loaded completely.
        If e.IsMainFrame Then
            e.Browser.ZoomLevel = 2.0
        End If
    End sub


The zoom level is configured for each domain separately, so if you set zoom level for thea.com web page, it will not be applied to theb.com web page.

Starting from DotNetBrowser 1.8.4 it is possible to disable zoom completely for a particular Browserinstance. See the Browser.ZoomEnabledproperty.


Example

C#

using DotNetBrowser;
using DotNetBrowser.Events;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ZoomSample
{
    class Program
    {
        static void Main(string[] args)
        {
            using (Browser browser = BrowserFactory.Create())
            {
                ManualResetEvent waitEvent = new ManualResetEvent(false);

                // Listen to zoom changed events
                browser.Context.ZoomService.ZoomChangedEvent += delegate(object sender, ZoomEventArgs e)
                {
                    Console.Out.WriteLine("e.Url = " + e.Url);
                    Console.Out.WriteLine("e.ZoomLevel = " + e.ZoomLevel);
                };


                browser.FinishLoadingFrameEvent += delegate(object sender, FinishLoadingEventArgs e)
                {
                    // Wait until main document of the web page is loaded completely.
                    if (e.IsMainFrame)
                    {
                        e.Browser.ZoomLevel = 2.0;
                        waitEvent.Set();
                    }
                };
                browser.LoadURL("http://www.teamdev.com");
                waitEvent.WaitOne();
            }
        }
    }
}


VB.NET 

Imports System.Threading
Imports DotNetBrowser
Imports DotNetBrowser.Events

Module Module1
    Sub Main()
        Using browser As Browser = BrowserFactory.Create()

            Dim waitEvent As ManualResetEvent = new ManualResetEvent(False)

            ' Listen to zoom changed events
            AddHandler browser.Context.ZoomService.ZoomChangedEvent,
                sub(sender As Object, e As ZoomEventArgs) 
                    Console.Out.WriteLine("e.Url = " + e.Url)
                    Console.Out.WriteLine("e.ZoomLevel = " + e.ZoomLevel.ToString())
                End sub

            AddHandler browser.FinishLoadingFrameEvent,
                sub(sender As Object, e As FinishLoadingEventArgs)
                    ' Wait until main document of the web page is loaded completely.
                    If e.IsMainFrame Then
                        e.Browser.ZoomLevel = 2.0
                        waitEvent.Set()
                    End If
                End sub

            browser.LoadURL("http://www.teamdev.com")
            waitEvent.WaitOne()
        End Using
    End Sub
End Module