c# – Dynamic Func,IOrderedQueryable> Expression

概述我正在使用这里提到的模式 http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application 我正在使用下面的方法来查询EF public virtual IEnum 我正在使用这里提到的模式
http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application

我正在使用下面的方法来查询EF

public virtual IEnumerable<TEntity> Get(        Expression<Func<TEntity,bool>> filter = null,Func<Iqueryable<TEntity>,IOrderedqueryable<TEntity>> orderBy = null,string includePropertIEs = "")    {        Iqueryable<TEntity> query = dbSet;        if (filter != null)        {            query = query.Where(filter);        }        foreach (var includeProperty in includePropertIEs.Split            (new char[] { ',' },StringSplitoptions.RemoveEmptyEntrIEs))        {            query = query.Include(includeProperty);        }        if (orderBy != null)        {            return orderBy(query).ToList();        }        else        {            return query.ToList();        }    }

现在我想创建动态Func< Iqueryable< TEntity>,IOrderedqueryable< TEntity>>表达式来订购我的数据.

我只知道字段名称为字符串和顺序类型(升序,降序)为字符串(asc,desc)

解决方法 最后我可以写出我想要的方法.

public static Func<Iqueryable<TEntity>,IOrderedqueryable<TEntity>> GetorderBy(string orderColumn,string orderType) {            Type typequeryable = typeof(Iqueryable<TEntity>);            ParameterExpression argqueryable = Expression.Parameter(typequeryable,"p");            var outerExpression = Expression.Lambda(argqueryable,argqueryable);            string[] props = orderColumn.Split('.');            Iqueryable<TEntity> query = new List<TEntity>().Asqueryable<TEntity>();            Type type = typeof(TEntity);            ParameterExpression arg = Expression.Parameter(type,"x");            Expression expr = arg;            foreach(string prop in props) {                PropertyInfo pi = type.GetProperty(prop,BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);                expr = Expression.Property(expr,pi);                type = pi.PropertyType;            }            LambdaExpression lambda = Expression.Lambda(expr,arg);            string methodname = orderType == "asc" ? "OrderBy" : "OrderByDescending";            MethodCallExpression resultExp =                Expression.Call(typeof(queryable),methodname,new Type[] { typeof(TEntity),type },outerExpression.Body,Expression.Quote(lambda));            var finalLambda = Expression.Lambda(resultExp,argqueryable);            return (Func<Iqueryable<TEntity>,IOrderedqueryable<TEntity>>)finalLambda.Compile();        }

此方法有两个参数,第一个是字段名,另一个是asc或desc.
方法的结果可以直接与Iqueryable对象一起使用.

谢谢你的帮助

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