编码的UI控件存在。 System.NullReferenceException

本文介绍了编码的UI控件存在。 System.NullReferenceException的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我想检查一些操作后该窗口是否存在。 我尝试：

I want to check that window exists after some actions. I try:

protected override Boolean IsPresent() { if (_mainWindow == null) { _mainWindow = new WinWindow(); _mainWindow.SearchProperties[WinWindow.PropertyNames.ControlName] = "MainWindow"; } return _mainWindow.Exists; }

但是如果控件不存在 mainWindow.Exists 抛出System.NullReferenceException。我不明白为什么会这样，因为此代码中的mainWindow引用不能为null。 如何验证_mainWindow是否成立？

But if control does not exist mainWindow.Exists throws System.NullReferenceException. I can't understand why it happens because mainWindow reference in this code can't be null. How can I verify is _mainWindow founded or not?

我已经完成了等待窗口加载并超时的操作。我也尝试使用 MainWindow.FindMainWindow（）。WaitForControlExist（100000），但它没有等待所需的超时。 此代码也未设置我所需的时间：

I've did it to wait for window loading with timeout. I've also tried to use MainWindow.FindMainWindow().WaitForControlExist(100000) but it doesn’t wait needed timeout. This code also not set my needed timout:

Playback.PlaybackSettings.SearchTimeout = 100000; Playback.PlaybackSettings.WaitForReadyTimeout = 100000;

我使用VS2013。

UPD：

这是我的NRE检查代码：

This is my code with NRE check:

protected override Boolean IsPresent() { if (_mainWindow == null) { _mainWindow = new WinWindow(); _mainWindow.SearchProperties[WinWindow.PropertyNames.ControlName] = "MainWindow"; } try { return _mainWindow.TryFind(); //TODO WTF? } catch (NullReferenceException e) { Console.WriteLine("We've got a NullReferenceException"); Console.WriteLine("_mainWindow reference is " + ((_mainWindow == null) ? "NULL" : "NOT NULL")); throw e; //Line 41 } }

这是结果：

We've got a NullReferenceException _mainWindow reference is NOT NULL Attachments: file:///Project/TestResults/User_WIN-FP7FMM7PUB1%202017-04-09%2015_57_34/In/4acd6ac8-92ce-4746-8787-3aecfd63bdd8/WIN-FP7FMM7PUB1/SuccessLoginTest.png Test method UITest.AutoTests.LoginTests.SuccessLoginTest threw exception: System.NullReferenceException: object reference not set to an instance of an object. in UITest.Locators.MainWindow.IsPresent() in MainWindow.cs: line 41 in UITest.Locators.BaseWindow.Wait() in BaseWindow.cs: line 34 in UITest.Locators.MainWindow..ctor() in MainWindow.cs: line 18 in UITest.Locators.LoginWindow.ClickEnterButton() in LoginWindow.cs: line 57 in UITest.AutoTests.LoginTests.SuccessLoginTest() in LoginTests.cs: line 32

推荐答案

问题出在版本中VS2013。 我已经安装了Update 5，如果没有找到对象，则TryFind（）返回False。

The problem was in version of VS2013. I have installed Update 5 and now TryFind() returns False if object not found.