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public static class QueryableExtension { public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> query, string propertyName) { return _OrderBy<T>(query, propertyName, false); } public static IOrderedQueryable<T> OrderByDescending<T>(this IQueryable<T> query, string propertyName) { return _OrderBy<T>(query, propertyName, true); } static IOrderedQueryable<T> _OrderBy<T>(IQueryable<T> 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<T>)method.Invoke(null, new object[] { query, memberProp }); } public static IOrderedQueryable<T> OrderByInternal<T, TProp>(IQueryable<T> query, PropertyInfo memberProperty) {//public return query.OrderBy(_GetLamba<T, TProp>(memberProperty)); } public static IOrderedQueryable<T> OrderByDescendingInternal<T, TProp>(IQueryable<T> query, PropertyInfo memberProperty) {//public return query.OrderByDescending(_GetLamba<T, TProp>(memberProperty)); } static Expression<Func<T, TProp>> _GetLamba<T, TProp>(PropertyInfo memberProperty) { if (memberProperty.PropertyType != typeof(TProp)) throw new Exception(); var thisArg = Expression.Parameter(typeof(T)); var lamba = Expression.Lambda<Func<T, TProp>>(Expression.Property(thisArg, memberProperty), thisArg); return lamba; } }
调用:
IQueryable<User> userQuery = ...; //正序 userQuery = userQuery.OrderBy("Code"); //降序 userQuery = userQuery.OrderByDescending("Code");