groupList是原始数据集合，List<T>

sortOrder是排序类型，desc 或者asc

sortName是排序属性名称

1.使用反射。

PRivate static object GetPropertyValue(object obj, string property)
{
      System.Reflection.PropertyInfo propertyInfo = obj.GetType().GetProperty(property);
      return propertyInfo.GetValue(obj, null);
} 

var resultList = sortOrder == "desc" ? groupList.OrderByDescending(p => GetPropertyValue(p, sortName)) : groupList.OrderBy(p => GetPropertyValue(p, sortName));

//linq方式：
//
var resultList1 = from p in groupList orderby GetPropertyValue(p, m.SortName) select p;

if (sortOrder == "desc")
    resultList1 = from p in groupList orderby GetPropertyValue(p, sortName) descending select p;

2.调用AsQueryable()

   将泛型 System.Collections.Generic.IEnumerable<T> 转换为泛型 System.Linq.IQueryable<T>。

var groupQueryList = groupList.AsQueryable();//here
var tmpList = groupQueryList.OrderBy(sortName, sortOrder);

需要如下扩展方法：

    public static IOrderedQueryable<T> OrderByDescending<T>(this IQueryable<T> source, string property)
    {
        return ApplyOrder<T>(source, property, "OrderByDescending");
    }
    public static IOrderedQueryable<T> ThenBy<T>(this IOrderedQueryable<T> source, string property)
    {
        return ApplyOrder<T>(source, property, "ThenBy");
    }
    public static IOrderedQueryable<T> ThenByDescending<T>(this IOrderedQueryable<T> source, string property)
    {
        return ApplyOrder<T>(source, property, "ThenByDescending");
    }
    static IOrderedQueryable<T> ApplyOrder<T>(IQueryable<T> source, string property, string methodName) {
        string[] props = property.Split('.');
        Type type = typeof(T);
        ParameterExpression arg = Expression.Parameter(type, "x");
        Expression expr = arg;
        foreach(string prop in props) {
            // use reflection (not ComponentModel) to mirror LINQ
            PropertyInfo pi = type.GetProperty(prop);
            expr = Expression.Property(expr, pi);
            type = pi.PropertyType;
        }
        Type delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
        LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);

        object result = typeof(Queryable).GetMethods().Single(
                method => method.Name == methodName
                        && method.IsGenericMethodDefinition
                        && method.GetGenericArguments().Length == 2
                        && method.GetParameters().Length == 2)
                .MakeGenericMethod(typeof(T), type)
                .Invoke(null, new object[] {source, lambda});
        return (IOrderedQueryable<T>)result;
   } 

参考：http://stackoverflow.com/questions/41244/dynamic-linq-orderby-on-ienumerablet#41262