CellContentClick throws ArgumentOutOfRangeException when user clicks on the column header

Problem In a WinForm project, you’re using a DataGridView control and are handling the CellContentClick event. When the user clicks the column header, the following exception is thrown: System.ArgumentOutOfRangeException: ‘Index was out of range. Must be non-negative and less than the size of the collection.Parameter name: index’ The problem is that when the user clicks … Read more

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

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# – Auto-populate a dropdown with enum values

When you need to show enum values in a dropdown, it’s a good idea to automatically populate the list, instead of manually setting all of the values. To autopopulate the dropdown, set the DataSource to Enum.Values(), like this: Then to get the option the user picked, do the following: When I launch my form, I … Read more

ArgumentOutOfRangeException: InvalidArgument=Value of 0 is not valid for SelectedIndex

Problem Let’s say you’re initializing a ComboBox like this: And you get the following exception: System.ArgumentOutOfRangeException: ‘InvalidArgument=Value of ‘0’ is not valid for ‘SelectedIndex’. (Parameter ‘value’)Actual value was 0.’ You’re getting this exception because the DataSource is empty. Solution Are you expecting there to always be data? If you’re expecting there to always be data, … Read more

WinForms: How to handle DataGridViewButtonColumn click event

There’s not a direct way to handle the DataGridViewButtonColumn button click event. Instead, you have to: Handle the DataGridView.CellContentClick event. Check if they clicked the button column. Execute the button click handling logic, passing in the bound data item. In this article I’ll show a step-by-step example of how to handle the button click. Example … Read more

WinForms: How to check if another form is open

If you’re working on a Windows Forms project and need to know which forms are open, use: This gives you an IEnumerable collection of form objects that are currently open. You can lookup a form by name, by type, or loop through the list. Example scenarios There are many scenarios where you’d want to know … Read more

Event-driven .NET: how events work

The very basis of event-driven programming is the concept of events. Events are an implementation of the Observer Pattern. With the Observer Pattern you have an observable entity and entities that want to observe that entity. Objects with events are observable, and other objects subscribe to those events and are notified when the events happen. … Read more