using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
	{
		public Form1()
		{
			InitializeComponent();

			this.Load += Form1_Load;
		}

		void Form1_Load(object sender, EventArgs e)
		{
			var list = GetSource().ToList();

			this.comboBox1.SetDataSource(
				list,
				_ => _.Key,
				_ => _.Value);
		}

		Dictionary<string, Assembly> GetSource()
		{
			return AppDomain.CurrentDomain.GetAssemblies()
				.ToDictionary(x => x.FullName, x => x);
		}
	}

	public static class Ex
	{
		public static void SetDataSource<T, TDisplayMember, TValueMember>(
			this ComboBox @this, IList<T> dataSource,
			Expression<Func<T, TDisplayMember>> displayMember,
			Expression<Func<T, TValueMember>> valueMember)
		{

			// _ => _.Key
			//      ^^^^^ この部分を取得
			var displayMemberBody = displayMember.Body as MemberExpression;
			if (displayMemberBody == null) throw new ArgumentException();

			// _ => _.Value
			//      ^^^^^^^ 同様にこの部分を取得
			var valueMemberBody = valueMember.Body as MemberExpression;
			if (valueMemberBody == null) throw new ArgumentException();

			@this.DataSource = dataSource;
			@this.DisplayMember = displayMemberBody.Member.Name;
			@this.ValueMember = valueMemberBody.Member.Name;
		}
	}
}