👀 Views: 0 💬 Answers: 1 📅 Created: 2025-06-18

winforms combobox data-binding nested-structures C#

I'm trying to implement I'm currently working on a WinForms application where I need to bind a ComboBox to a nested data structure. My data model consists of a `Department` class that contains a list of `Employee` objects. Each `Employee` has properties for `Name` and `Id`. I've set up the binding like this: ```csharp public class Department { public string Name { get; set; } public List<Employee> Employees { get; set; } } public class Employee { public string Name { get; set; } public int Id { get; set; } } var departments = new List<Department> { new Department { Name = "HR", Employees = new List<Employee> { new Employee { Name = "Alice", Id = 1 }, new Employee { Name = "Bob", Id = 2 } } }, new Department { Name = "IT", Employees = new List<Employee> { new Employee { Name = "Charlie", Id = 3 }, new Employee { Name = "David", Id = 4 } } } }; comboBoxDepartments.DataSource = departments; comboBoxDepartments.DisplayMember = "Name"; comboBoxDepartments.ValueMember = "Id"; ``` Despite this setup, I am encountering an issue where the `ComboBox` is not displaying the department names as expected. Instead, it shows the result of the `ToString()` method, which defaults to the type name. When I select a department, it doesn't seem to store or reflect the selected value properly, leading to further confusion in my application logic. I've tried explicitly setting the `DataSource` to the `Employees` list after selecting a department, like this: ```csharp comboBoxEmployees.DataSource = ((Department)comboBoxDepartments.SelectedItem)?.Employees; comboBoxEmployees.DisplayMember = "Name"; comboBoxEmployees.ValueMember = "Id"; ``` This results in a `NullReferenceException` when I attempt to access `SelectedItem` before any selection is made. I'm not sure how to handle the binding without causing these issues. Any help or advice on best practices for binding nested structures in a WinForms application would be greatly appreciated! My team is using C# for this service.