Expressionからプロパティ名を取得するサンプル

ExpressionHelperTest.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using Xunit;
using System.Linq.Expressions;

namespace Test {
	public static class ExpressionHelper {
		// "@object => new { @object.property1, @object.property2 }"の式からプロパティ名を取得
		public static IEnumerable<string> GetMemberNames<TSource>(Expression<Func<TSource, object>> expression) {
			if (expression.Body is NewExpression @new) {
				return @new.Members.Select(member => member.Name);
			}

			return Enumerable.Empty<string>();
		}

		// "@object => @object.property"の式からプロパティ名を取得
		public static string GetMemberName<TSource>(Expression<Func<TSource, object>> expression) {
			if (expression.Body is MemberExpression member) {
				return member.Member.Name;

			} else if (expression.Body is UnaryExpression unary) {
				// プロパティが値型の場合はBOX化されるため？
				if (unary.NodeType == ExpressionType.Convert &&
					unary.Operand is MemberExpression operand) {
					return operand.Member.Name;
				}
			}

			// nullで良いか悩む
			return null;
		}
	}

	// テスト用
	public class Item {
		public int Id { get; set; }
		public string Name { get; set; }
	}

	public class ExpressionHelperTest {
		[Fact]
		public void GetMemberNames_匿名オブジェクトを生成する式からメンバー名一覧を取得() {
			var members = ExpressionHelper.GetMemberNames<Item>(item => new { item.Id, item.Name });

			Assert.Collection(members,
				member => Assert.Equal("Id", member),
				member => Assert.Equal("Name", member));
		}

		[Fact]
		public void GetMemberName_参照型のプロパティにアクセスする式からプロパティ名を取得() {
			var member = ExpressionHelper.GetMemberName<Item>(item => item.Name);

			Assert.Equal("Name", member);
		}

		[Fact]
		public void GetMemberName_値型のプロパティにアクセスする式からプロパティ名を取得() {
			var member = ExpressionHelper.GetMemberName<Item>(item => item.Id);

			Assert.Equal("Id", member);
		}
	}
}