WinForms – How to prompt the user for a file

In a WinForms project, you can prompt the user to select a file by using the OpenFileDialog control: When you call ShowDialog(), it’ll prompt the user to select a file: When the user clicks Open, you’ll be able to get the file path they selected from the OpenFileDialog.FileName property. To use the OpenFileDialog control, drag … Read more

WinForms – How to remove checked items from CheckedListBox

Normally the items in a CheckedListBox are hardcoded or added programmatically (from an enum, or from some data source). But sometimes you may want to allow the user to add and remove items from a CheckedListItem. In this article I’ll show how to add items and remove them. I’ll be working with text, and will … Read more

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 – How to programmatically check items in CheckedListBox

A CheckedListBox allows the user to check one or more checkboxes. Sometimes you’ll want to be able to check the boxes programmatically. For example, you may want to allow the user to check or uncheck all boxes at once. Or perhaps you want to persist the values the user checked and load them later. To … 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

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