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@gicque
Created June 24, 2015 18:16
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cefsharp.OffScreen.Example: EvaluateScriptAsync result in System.NullReferenceException
// Copyright © 2010-2015 The CefSharp Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
using System;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.Threading.Tasks;
using CefSharp.Example;
namespace CefSharp.OffScreen.Example
{
public class Program
{
private const string TestUrl = "https://www.google.com/";
public static void Main(string[] args)
{
Console.WriteLine("This example application will load {0}, take a screenshot, and save it to your desktop.", TestUrl);
Console.WriteLine("You may see a lot of Chromium debugging output, please wait...");
Console.WriteLine();
// You need to replace this with your own call to Cef.Initialize();
CefExample.Init();
MainAsync();
// We have to wait for something, otherwise the process will exit too soon.
Console.ReadKey();
// Clean up Chromium objects. You need to call this in your application otherwise
// you will get a crash when closing.
Cef.Shutdown();
}
private static async void MainAsync()
{
// Create the offscreen Chromium browser.
using (var browser = new ChromiumWebBrowser(TestUrl))
{
await LoadPageAsync(browser);
// Wait for the screenshot to be taken.
await browser.ScreenshotAsync().ContinueWith(DisplayBitmap);
await LoadPageAsync(browser, "http://github.com");
// Wait for the screenshot to be taken.
await browser.ScreenshotAsync().ContinueWith(DisplayBitmap);
var res = await browser.EvaluateScriptAsync("1 + 1");
Debugger.Break();
}
}
public static Task LoadPageAsync(IWebBrowser browser, string address = null)
{
var tcs = new TaskCompletionSource<bool>();
EventHandler<LoadingStateChangedEventArgs> handler = null;
handler = (sender, args) =>
{
//Wait for while page to finish loading not just the first frame
if (!args.IsLoading)
{
browser.LoadingStateChanged -= handler;
tcs.TrySetResult(true);
}
};
browser.LoadingStateChanged += handler;
if (!string.IsNullOrEmpty(address))
{
browser.Load(address);
}
return tcs.Task;
}
private static void DisplayBitmap(Task<Bitmap> task)
{
// Make a file to save it to (e.g. C:\Users\jan\Desktop\CefSharp screenshot.png)
var screenshotPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "CefSharp screenshot" + DateTime.Now.Ticks + ".png");
Console.WriteLine();
Console.WriteLine("Screenshot ready. Saving to {0}", screenshotPath);
var bitmap = task.Result;
// Save the Bitmap to the path.
// The image type is auto-detected via the ".png" extension.
bitmap.Save(screenshotPath);
// We no longer need the Bitmap.
// Dispose it to avoid keeping the memory alive. Especially important in 32-bit applications.
bitmap.Dispose();
Console.WriteLine("Screenshot saved. Launching your default image viewer...");
// Tell Windows to launch the saved image.
Process.Start(screenshotPath);
Console.WriteLine("Image viewer launched. Press any key to exit.");
}
}
}
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