转载的代码，改天再研究
public PageData<T> FindAll(int PageIndex, int PageSize, Expression<Func<T, bool>> condition, String orderByExpression, bool IsDESC)
{
var property = typeof(T).GetProperty(orderByExpression);
var parameter = Expression.Parameter(typeof(T), "p");
var propertyAccess = Expression.MakeMemberAccess(parameter, property);
var orderByExp = Expression.Lambda(propertyAccess, parameter);
var query = (Data.CreateObjectSet<T>()).Where(condition);
string methodName = IsDESC ? "OrderByDescending" : "OrderBy";
MethodCallExpression resultExp = Expression.Call(typeof(Queryable), methodName, new Type[] { typeof(T), property.PropertyType }, query.Expression, Expression.Quote(orderByExp));
query = query.Provider.CreateQuery<T>(resultExp);
PageData<T> pageData = new PageData<T>();
pageData.TotalCount = query.Count();
pageData.DataList = query.Skip((PageIndex - 1) * PageSize).Take(PageSize).ToList();
ObjectQuery<T> ss = query as ObjectQuery<T>;
String sss = ss.ToTraceString();
return pageData;
}