How do I add values to a DataGridViewComboBoxColumn DataSource?

Question

I have an issue wherein I have a DataGridViewComboBoxColumn in a DataGridView and I want to add an item to the DataSource.

I've initially set the DataSource property to a List<string> which works fine. Later I'll add an item to this list, which works fine. But when I try to choose this item in a combobox, I get a data validation error,

System.ArgumentException: DataGridViewComboBoxCell value is not valid.

Further, I can't actually set the combobox to the newly added value.

Here is a fully working example.

public partial class Form1 : Form
{
    List<string> Data { get; set; }

    public Form1()
    {
        InitializeComponent();

        // Populate our data source
        this.Data = new List<string> { "Thing1", "Thing2" };

        // Set up controls
        var gvData = new System.Windows.Forms.DataGridView();
        var col1 = new System.Windows.Forms.DataGridViewComboBoxColumn();
        var button = new System.Windows.Forms.Button();

        gvData.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] { col1 });

        // Set the column's DataSource
        col1.DataSource = this.Data;
        col1.HeaderText = "Test";
        col1.Name = "col1";

        // Set up a button which adds something to the source
        button.Text = "Add";
        button.Location = new System.Drawing.Point(0, 200);
        button.Click += (e, s) => this.Data.Add("Thing3");

        this.Controls.Add(gvData);
        this.Controls.Add(button);
    }
}

How can I add items to the DataSource for my DataGridViewComboBoxColumn?

Answer 1

Changing

button.Click += (e, s) => this.Data.Add("Thing3");

to

           button.Click += (e, s) =>
           {
                col1.DataSource = null;
                this.Data.Add("Thing3");
                col1.DataSource = Data;
           };

has worked for me.