Custom column names for DataGridView with associated DataSource

Use the DisplayName attribute on your properties to specify column names in your DataGridView:

class Key
{
    [System.ComponentModel.DisplayName("Key")]
    public string Value { get; }
    [System.ComponentModel.DisplayName("Expire")]
    public DateTime ExpirationDate { get; }
} 

You should be able to change the header cells after you've set the datasource:

    if (dataGridView1.Columns["Value"] != null)
        dataGridView1.Columns["Value"].HeaderText = "Key";
    if (dataGridView1.Columns["Expiration"] != null)
        dataGridView1.Columns["Expiration"].HeaderText = "Expire";