Ошибка в ComboBox после добавления источника данных

public class DemoSource
    {
         public static List<Types> _types = new List<Types>
        {
           Тут добавляю пару элементов типа Types
        };
        public class Types
        {
            public string Name { get; set; }
            public int Id { get; set; }
        }
    }

 this.comboBox.DataSource = _types;
 this.comboBox.DisplayMember = "Name";
 this.comboBox.ValueMember = "Id";

this.comboBox.DataSource = DemoSource._types;
this.comboBox.DisplayMember = "Name";
this.comboBox.ValueMember = "Id";

this.comboBox.DataSource = DemoSource._types;
this.comboBox.DisplayMember = "Name";
this.comboBox.ValueMember = "Id";

this.comboBox.DataSource = new BindingSource(_types, null);

public static class DemoSource
{
 
    public static List<Types> _types;
    static DemoSource()
    {
        _types = new List<Types>();
        _types.Add(new Types(){Name="qqq", Id=1});
        _types.Add(new Types(){Name="wwww", Id=2});
        _types.Add(new Types(){Name="eee", Id=3});
        _types.Add(new Types(){Name="rrr", Id=4});
    }
 
    public class Types
    {
        public string Name { get; set; }
        public int Id { get; set; }
    }
}

this.comboBox1.DataSource = DemoSource._types;
this.comboBox1.DisplayMember = "Name";
this.comboBox1.ValueMember = "Id";

// 
// comboBox1
// 
this.comboBox1.DisplayMember = "Name";
this.comboBox1.FormattingEnabled = true;
types1.Id = 1;
types1.Name = "qqq";
types2.Id = 2;
types2.Name = "wwww";
types3.Id = 3;
types3.Name = "eee";
types4.Id = 4;
types4.Name = "rrr";
this.comboBox1.Items.AddRange(new object[] {
types1,
types2,
types3,
types4});
this.comboBox1.Location = new System.Drawing.Point(123, 29);
this.comboBox1.Name = "comboBox1";
this.comboBox1.Size = new System.Drawing.Size(180, 21);
this.comboBox1.TabIndex = 1;
this.comboBox1.ValueMember = "Id";

(comboBox1.SelectedItem as DemoSource.Types).Id