event

C# – Unit test an event handler

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An event handler is a method that is registered to listen to an event. When the event is invoked, the event handler method is called. You may be tempted to directly call the event handler to unit test it. It’s better to actually raise the event though, and then check the side effects of the … Read more

Invoke or BeginInvoke cannot be called on a control until the window handle has been created

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Problem In a WinForms project, if you try to call Invoke/BeginInvoke before the window handle is created, you’ll get the following exception: System.InvalidOperationException: Invoke or BeginInvoke cannot be called on a control until the window handle has been created Because this exception happens while the form is initializing, it typically results in the form not … Read more

C# – How to use FileSystemWatcher

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You can use the FileSystemWatcher class to detect file system changes, such as when a file is created, deleted, modified, or renamed. When a change happens, it raises an event that you can handle. This is an event-based alternative to polling for file changes. In this article, I’ll show how to use FileSystemWatcher to detect … Read more

WinForms: How to handle DataGridViewButtonColumn click event

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Here’s how to handle the DataGridViewButtonColumn button click event: In this article I’ll show a step-by-step example of how to handle the button click. Example DataGridView with a button column When I click the button I want it to say Hi to the person. 1 – Set the DataSource to BindingList<Person> 2 – Add ClickHandler(Person … Read more

C# – Monitor data changes with SQL Server query notifications

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You can use SQL Server query notifications to send push notifications to your code when data changes. This is an alternative to polling the database for changes. In this article, I’ll show how to configure this feature and work with it in the code. 1 – Enable Service Broker and configure permissions You need to … Read more