网上看到的：
class Program
{
static List<User> list = new List<User>()
{
new User(){ID=1,Name="Hello",Age=17,Hobby="a"},
new User(){ID=2,Name="Boy",Age=50,Hobby="z"},
new User(){ID=3,Name="Girl",Age=33,Hobby="x"},
new User(){ID=4,Name="Fox",Age=43,Hobby="b"},
new User(){ID=5,Name="Fire",Age=17,Hobby="f"},
};
static void Main(string[] args)
{
var q = list.AsQueryable().OrderBy("Name", true);
q.ToList().ForEach(x => Console.WriteLine(string.Format("ID:{0},Name:{1},Age:{2},Hobby:{3}", x.ID, x.Name, x.Age, x.Hobby)));
Console.ReadLine();
}
}
public class User
{
public int ID { get; set; }
public string Name { get; set; }
public int Age { get; set; }
public string Hobby { get; set; }
}
//动态表达式
public static class Test
{
public static IQueryable<TEntity> OrderBy<TEntity>(this IQueryable<TEntity> source, string propertyName,
bool asc = true) where TEntity : class
{
string command = asc ? "OrderBy" : "OrderByDescending";
var type = typeof(TEntity);
var property = type.GetProperty(propertyName);
var parameter = Expression.Parameter(type, "p");
var propertyAccess = Expression.MakeMemberAccess(parameter, property);
var orderByExpression = Expression.Lambda(propertyAccess, parameter);
var resultExpression = Expression.Call(typeof(Queryable), command, new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExpression));
return source.Provider.CreateQuery<TEntity>(resultExpression);
}
}