Lambda类型参数必须派生自系统。委派

在一个 C#

我发现了 magic Gist var lambda = ... 一直抛出以下错误

Lambda类型参数必须派生自系统。委派

这是密码

public static IQueryable<dynamic> ToDynamic<T>(this IQueryable<T> query, IEnumerable<String> fields)
{
    var pocoType = typeof(T);

    var itemParam = Expression.Parameter(pocoType, "x");
    var members = fields.Select(f => Expression.PropertyOrField(itemParam, f));
    var addMethod = typeof(IDictionary<string, object>).GetMethod(
                "Add", new Type[] { typeof(string), typeof(object) });


    var elementInits = members.Select(m => Expression.ElementInit(addMethod, Expression.Constant(m.Member.Name), Expression.Convert(m, typeof(object))));

    var expando = Expression.New(typeof(ExpandoObject));
    var lambda = Expression.Lambda<Expression<Func<T, dynamic>>>(Expression.ListInit(expando, elementInits), itemParam);

    return query.Select(lambda.Compile());
}