使用linq的OrderBy，如果明确知道是哪个字段，当然很容易：

IQueryable
     
       userQuery = ...; userQuery.OrderBy(u => u.Code)
     

但假如我们想写一个通用方法，预先并不知道要用哪个字段排序呢？

在网上寻寻觅觅，有许多国内的博客互相抄袭，信誓旦旦，但其实那些代码都运行不了。

还是老外的好使：

我拿来修改了一下，可以用。主要思想是扩展Queryable。但里面的东西有许多我都看不懂。

public static class QueryableExtension    {        public static IOrderedQueryable
     
       OrderBy
      
       (this IQueryable
       
         query, string propertyName)        {            return _OrderBy
        
         (query, propertyName, false);        }        public static IOrderedQueryable
         
           OrderByDescending
          
           (this IQueryable
           
             query, string propertyName) { return _OrderBy
            
             (query, propertyName, true); } static IOrderedQueryable
             
               _OrderBy
              
               (IQueryable
               
                 query, string propertyName,bool isDesc) { string methodname = (isDesc) ? "OrderByDescendingInternal" : "OrderByInternal"; var memberProp = typeof(T).GetProperty(propertyName); var method = typeof(QueryableExtension).GetMethod(methodname) .MakeGenericMethod(typeof(T), memberProp.PropertyType); return (IOrderedQueryable
                
                 )method.Invoke(null, new object[] { query, memberProp }); } public static IOrderedQueryable
                 
                   OrderByInternal
                  
                   (IQueryable
                   
                     query, PropertyInfo memberProperty) { //public return query.OrderBy(_GetLamba
                    
                     (memberProperty)); } public static IOrderedQueryable
                     
                       OrderByDescendingInternal
                      
                       (IQueryable
                       
                         query, PropertyInfo memberProperty) { //public return query.OrderByDescending(_GetLamba
                        
                         (memberProperty)); } static Expression
                         
                          
                           > _GetLamba
                           
                            (PropertyInfo memberProperty) { if (memberProperty.PropertyType != typeof(TProp)) throw new Exception(); var thisArg = Expression.Parameter(typeof(T)); var lamba = Expression.Lambda
                            
                             
                              >(Expression.Property(thisArg, memberProperty), thisArg); return lamba; } }
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

调用：

IQueryable
     
       userQuery = ...;//正序userQuery = userQuery.OrderBy("Code");//降序userQuery = userQuery.OrderByDescending("Code");