Navigation

This guide describes the navigation events and shows how to load URLs and files, filter navigation requests, work with navigation history, and so on.

Loading URL

To navigate to a resource identified by a URL, use one of the following methods:

  • INavigation.LoadUrl(string url)
  • INavigation.LoadUrl(LoadUrlParameters parameters)

Example below shows how to navigate to https://www.google.com using the INavigation.LoadUrl(string) method:

INavigation navigation = browser.Navigation;
navigation.LoadUrl("https://www.google.com");
Dim navigation As INavigation = browser.Navigation
navigation.LoadUrl("https://www.google.com")

Loading URL synchronously

The LoadUrl method sends a navigation request to the given resource and returns a Task<LoadResult> that can be used to wait until the resource is considered to be loaded completely.

If you need to block the current thread execution until the resource is loaded completely, use the Task.Wait() method:

navigation.LoadUrl("https://www.google.com").Wait();
navigation.LoadUrl("https://www.google.com").Wait()

This method blocks the current thread execution until the main frame of the resource is loaded completely or until the default 100 seconds timeout is reached.

If the navigation fails, the returned Task<LoadResult> is completed, and its Task.Result property returns LoadResult.Failed.

If the resource is not loaded within a given period, the TimeoutException exception occurs.

The web page is considered to be loaded completely when at least one of the following events, namely, FrameLoadFinished, NavigationFinished, or FrameLoadFailed occurs for the main frame.

Loading URL with POST

To load a web page by its URL and send POST data, use the INavigation.LoadUrl(LoadUrlParameters) method. The following code demonstrates how to load URL and send POST data in different formats using extra headers.

You can send a web form data in the key=value format to a web server:

navigation.LoadUrl(new LoadUrlParameters("https://postman-echo.com/post")
{
    PostData = "key=value",
    HttpHeaders = new HttpHeader[]
    {
        new HttpHeader("Content-Type", "application/x-www-form-urlencoded")
    }
});
navigation.LoadUrl(New LoadUrlParameters("https://postman-echo.com/post") With {
    .PostData = "key=value",
    .HttpHeaders =
    {
        New HttpHeader("Content-Type", "application/x-www-form-urlencoded")
    }
})

You need to specify explicitly “Content-Type” header for each request type.

If you want to send some plain text, add the extra headers that instruct the web server it is a plain text:

navigation.LoadUrl(new LoadUrlParameters("https://postman-echo.com/post")
{
    PostData = "Some text...",
    HttpHeaders = new[]
    {
        new HttpHeader("Content-Type", "text/plain")
    }
});
navigation.LoadUrl(New LoadUrlParameters("https://postman-echo.com/post") With {
    .PostData = "Some text...",
    .HttpHeaders = 
    { 
        New HttpHeader("Content-Type", "text/plain") 
    }
})

You can send any data of various types. To do so, specify its Content-Type. See the code sample on sending JSON data below:

navigation.LoadUrl(new LoadUrlParameters("https://postman-echo.com/post")
{
    PostData = "{\"title\":\"Hello\"}",
    HttpHeaders = new[]
    {
        new HttpHeader("Content-Type", "application/json")
    }
});
navigation.LoadUrl(New LoadUrlParameters("https://postman-echo.com/post") With {
    .PostData = "{""title"":""Hello""}",
    .HttpHeaders = 
    { 
        New HttpHeader("Content-Type", "application/json") 
    }
})

Loading a file

You can use the same methods to load HTML files from the local file system by providing an absolute path to the HTML file instead of an URL. See the code sample below:

navigation.LoadUrl(Path.GetFullPath("index.html"));
navigation.LoadUrl(Path.GetFullPath("index.html"))

Loading HTML

To load HTML into browser, you can create a data: encoded URI and then load it using the regular LoadUrl call. Here is an example:

var html = "<html><head></head><body><h1>Html Encoded in URL!</h1></body></html>";
var base64EncodedHtml = Convert.ToBase64String(Encoding.UTF8.GetBytes(html));
browser.Navigation.LoadUrl("data:text/html;base64," + base64EncodedHtml).Wait();
Dim html = "<html><head></head><body><h1>Html Encoded in URL!</h1></body></html>"
Dim base64EncodedHtml = Convert.ToBase64String(Encoding.UTF8.GetBytes(html))
browser.Navigation.LoadUrl("data:text/html;base64," & base64EncodedHtml).Wait()

Chromium limits data-encoded URIs to a maximum length of 2MB.

However, the base URL cannot be set when using this approach.

Another possible approach is to register a Scheme with a handler and intercept the corresponding request to provide the HTML. See the corresponding article.

Reloading

There are several options to reload the currently loaded web page:

  • Reload using HTTP cache:
navigation.Reload();
navigation.Reload()
  • Reload ignoring HTTP cache:
navigation.ReloadIgnoringCache();
navigation.ReloadIgnoringCache()
  • Reload using HTTP cache and check for repost:
navigation.ReloadAndCheckForRepost();
navigation.ReloadAndCheckForRepost()
  • Reload ignoring HTTP cache and check for repost:
navigation.ReloadIgnoringCacheAndCheckForRepost();
navigation.ReloadIgnoringCacheAndCheckForRepost()

Stopping

Use the INavigation.Stop() method to cancel any pending navigation or download operation, and stop any dynamic page elements, such as background sounds and animations. See the code sample below:

navigation.Stop();
navigation.Stop()

Back & forward

DotNetBrowser allows working with the navigation back-forward history list.

When you create an IBrowser instance, it navigates to the about:blank web page by default. There is always one entry in the navigation back-forward list.

To load the previous location in the back-forward list, use the following approach:

if (navigation.CanGoBack()) {
    navigation.GoBack();
}
If navigation.CanGoBack() Then
    navigation.GoBack()
End If

To load the next location in the back-forward list, use the following approach:

if (navigation.CanGoForward()) {
    navigation.GoForward();
}
If navigation.CanGoForward() Then
    navigation.GoForward()
End If

To navigate to the entry at a specific index in the back-forward list, use the following approach:

if (index >=0 && index < navigation.EntryCount) {
    navigation.GoTo(index);
}
If index >=0 AndAlso index < navigation.EntryCount Then
    navigation.GoTo(index)
End If

To go through the back-forward list and get the details about every navigation entry, use the following approach:

for (int index = 0; index < navigation.EntryCount; index++) {
    INavigationEntry navigationEntry = navigation.EntryAt(index);
    Console.WriteLine("URL: " + navigationEntry.Url);
    Console.WriteLine("Title: " + navigationEntry.Title);
}
For index As Integer = 0 To navigation.EntryCount - 1
    Dim navigationEntry As INavigationEntry = navigation.EntryAt(index)
    Console.WriteLine("URL: " & navigationEntry.Url)
    Console.WriteLine("Title: " & navigationEntry.Title)
Next

To modify the back-forward list by removing the entries, use the following approach:

// Returns the number of entries in the back/forward list.
int entryCount = navigation.EntryCount;
// Remove navigation entries at index.
for (int i = entryCount - 2; i >= 0; i--) {
    bool success = navigation.RemoveEntryAt(i);
    Console.WriteLine("Navigation entry at index " + i +
            " has been removed successfully? " + success);
}
' Returns the number of entries in the back/forward list.
Dim entryCount As Integer = navigation.EntryCount
' Remove navigation entries at index.
For i As Integer = entryCount - 2 To 0 Step -1
    Dim success As Boolean = navigation.RemoveEntryAt(i)
    Console.WriteLine("Navigation entry at index " & i & 
                      " has been removed successfully? " & success)
Next

Overscroll history navigation

In the hardware-accelerated rendering mode, DotNetBrowser allows navigating back/forward with a left/right swipe on devices with the touch screen. By default, the overscroll navigation is disabled. To enable it, use the IBrowserSettings.OverscrollHistoryNavigationEnabled property:

browser.Settings.OverscrollHistoryNavigationEnabled = true;
browser.Settings.OverscrollHistoryNavigationEnabled = True

Filtering URLs

You can decide whether navigation request to a specific URL is ignored.

See the code sample below showing how to ignore navigation requests to all URLs starting with https://www.google:

navigation.StartNavigationHandler = 
    new Handler<StartNavigationParameters, StartNavigationResponse>((p) =>
    {
        // Ignore navigation requests to the URLs that start 
        // with "https://www.google"
        if (p.Url.StartsWith("https://www.google"))
        {
            return StartNavigationResponse.Ignore();
        }
        return StartNavigationResponse.Start();
    });
navigation.StartNavigationHandler = 
    New Handler(Of StartNavigationParameters, StartNavigationResponse)(Function(p)
        ' Ignore navigation requests to the URLs that start
        ' with "https://www.google".
        If p.Url.StartsWith("https://www.google") Then
            Return StartNavigationResponse.Ignore()
        End If
        Return StartNavigationResponse.Start()
    End Function)

Filtering resources

The SendUrlRequestHandler handler lets you determine whether the resources such as HTML, image, JavaScript or CSS file, favicon, and others are loaded. By default, all resources are loaded. To modify the default behavior, register your own handler implementation where you decide which resources are canceled or loaded.

See the code sample below showing how to suppress all images:

engine.Network.SendUrlRequestHandler =
    new Handler<SendUrlRequestParameters, SendUrlRequestResponse>(p =>
    {
        if (p.UrlRequest.ResourceType == ResourceType.Image)
        {
            return SendUrlRequestResponse.Cancel();
        }
        return SendUrlRequestResponse.Continue();
    });
engine.Network.SendUrlRequestHandler = 
    New Handler(Of SendUrlRequestParameters, SendUrlRequestResponse)(Function(p)
        If p.UrlRequest.ResourceType = ResourceType.Image Then
            Return SendUrlRequestResponse.Cancel()
        End If
        Return SendUrlRequestResponse.Continue()
    End Function)

Loading a web page is a complex process where navigation events are fired. The following diagram shows the order of the navigation events that might be fired when loading a web page: Navigation Events Flow

Load started

To get notifications when content loading has started, use the LoadStarted event. See the code sample below:

navigation.LoadStarted += (s, e) => {};
AddHandler navigation.LoadStarted, Sub(s, e)
End Sub

This event corresponds to the moment when the spinner of the tab starts spinning.

Load finished

To get notifications when content loading has finished, use the LoadFinished event. For example:

navigation.LoadFinished += (s, e) => {};
AddHandler navigation.LoadFinished, Sub(s, e)
End Sub

This event corresponds to the moment when the spinner of the tab stops spinning.

Load progress

The LoadProgressChanged event allows getting notifications about load progress:

navigation.LoadProgressChanged += (s, e) =>
{
    // The value indicating the loading progress of the web page.
    double progress = e.Progress;
};
AddHandler navigation.LoadProgressChanged, Sub(s, e)
    ' The value indicating the loading progress of the web page.
    Dim progress As Double = e.Progress
End Sub

To get notifications when navigation has started, use the NavigationStarted event. See the code sample below:

navigation.NavigationStarted += (s, e) => 
{
    string url = e.Url;
    // Indicates whether the navigation will be performed
    // in the scope of the same document.
    bool isSameDocument = e.IsSameDocument;
};
AddHandler navigation.NavigationStarted, Sub(s, e)
    Dim url As String = e.Url
    ' Indicates whether the navigation will be performed
    ' in the scope of the same document.
    Dim isSameDocument As Boolean = e.IsSameDocument
End Sub

To get notifications when navigation has stopped, use the NavigationStopped event. See the code sample below:

navigation.NavigationStopped += (s, e) => {};
AddHandler navigation.NavigationStopped, Sub(s, e)
End Sub

This event is fired when navigation is stopped using the Navigation.stop() method.

To get notifications when navigation has been redirected to a new URL, use the NavigationRedirected event. See the code sample below:

navigation.NavigationRedirected += (s, e) => {
    // The navigation redirect URL.
    string url = e.Url;
};
AddHandler navigation.NavigationRedirected, Sub(s, e)
    ' The navigation redirect URL.
    Dim url As String = e.Url
End Sub

To get notifications when navigation has finished, use the NavigationFinished event. See the code sample below:

navigation.NavigationFinished += (s, e) => {
    string url = e.Url;
    IFrame frame = e.Frame;
    bool hasCommitted = e.HasCommitted;
    bool isSameDocument = e.IsSameDocument;
    bool isErrorPage = e.IsErrorPage;
    if (isErrorPage) {
        NetError error = e.ErrorCode;
    }
};
AddHandler navigation.NavigationFinished, Sub(s, e)
    Dim url As String = e.Url
    Dim frame As IFrame = e.Frame
    Dim hasCommitted As Boolean = e.HasCommitted
    Dim isSameDocument As Boolean = e.IsSameDocument
    Dim isErrorPage As Boolean = e.IsErrorPage
    If isErrorPage Then
        Dim [error] As NetError = e.ErrorCode
    End If
End Sub

This event is fired when navigation is committed, aborted, or replaced by a new one. To know if the navigation has committed, use NavigationFinishedEventArgs.HasCommitted. To know if the navigation resulted in an error page, use NavigationFinishedEventArgs.IsErrorPage.

If the event is called because the navigation committed, the document load will still be ongoing.

The event is fired by same-document (in the scope of the same document) navigations, such as fragment navigations or window.history.pushState()/window.history.replaceState(), which does not result in a document change. Use NavigationFinishedEventArgs.IsSameDocument property to check if it is a same-document navigation.

Frame load finished

To get notifications when content loading in the IFrame has finished, use the FrameLoadFinished event. See the code sample below:

navigation.FrameLoadFinished += (s, e) =>
{
    string url = e.ValidatedUrl;
    IFrame frame = e.Frame;
};
AddHandler navigation.FrameLoadFinished, Sub(s, e)
    Dim url As String = e.ValidatedUrl
    Dim frame As IFrame = e.Frame
End Sub

This event corresponds to the moment when the content in the Frame has been loaded completely.

Frame load failed

To get notifications when content loading in the Frame has failed for some reason, use the FrameLoadFailed event. See the code sample below:

navigation.FrameLoadFailed += (s, e) =>
{
    string url = e.ValidatedUrl;
    NetError error = e.ErrorCode;
};
AddHandler navigation.FrameLoadFailed, Sub(s, e)
    Dim url As String = e.ValidatedUrl
    Dim [error] As NetError = e.ErrorCode
End Sub

Frame document load finished

To get notifications when the document loading in the Frame has finished, use the FrameDocumentLoadFinished event. See the code sample below:

navigation.FrameDocumentLoadFinished += (s, e) => 
{
    IFrame frame = e.Frame;
};
AddHandler navigation.FrameDocumentLoadFinished, Sub(s, e)
    Dim frame As IFrame = e.Frame
End Sub

At this point, deferred scripts were executed, and the content scripts marked document_end get injected into the frame.

Custom error page

To override standard Chromium error pages, use ShowHttpErrorPageHandler and ShowNetErrorPageHandler handlers for HTTP (e.g. 404 Not Found) or network errors (e.g. ERR_CONNECTION_REFUSED) respectively. See examples below:

HTTP error page

browser.Navigation.ShowHttpErrorPageHandler =
    new Handler<ShowHttpErrorPageParameters, ShowHttpErrorPageResponse>(arg =>
    {
        string url = arg.Url;
        HttpStatusCode httpStatusCode = arg.HttpStatus;
        return ShowHttpErrorPageResponse.Show("HTTP Error web page:" + httpStatusCode);
    });
browser.Navigation.ShowHttpErrorPageHandler = 
    New Handler(Of ShowHttpErrorPageParameters, ShowHttpErrorPageResponse)(Function(arg)
        Dim url As String = arg.Url
        Dim httpStatusCode As HttpStatusCode = arg.HttpStatus
        Return ShowHttpErrorPageResponse.Show("HTTP Error web page:" & httpStatusCode)
    End Function)

Network error page

browser.Navigation.ShowNetErrorPageHandler = 
    new Handler<ShowNetErrorPageParameters, ShowNetErrorPageResponse>(arg =>
    {
        return ShowNetErrorPageResponse.Show("Network error web page");
    });
browser.Navigation.ShowNetErrorPageHandler = 
    New Handler(Of ShowNetErrorPageParameters, ShowNetErrorPageResponse)(Function(arg)
        Return ShowNetErrorPageResponse.Show("Network error web page")
    End Function)

Custom error pages provided by the servers are not intercepted by these handlers and cannot be overridden using this functionality. The above handlers are invoked only for overriding the default Chromium error pages.

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