C# linq查詢之靜態OrderBy用法實例。本站提示廣大學習愛好者:(C# linq查詢之靜態OrderBy用法實例)文章只能為提供參考,不一定能成為您想要的結果。以下是C# linq查詢之靜態OrderBy用法實例正文
本文實例講述了C# linq查詢之靜態OrderBy用法。分享給年夜家供年夜家參考。詳細剖析以下:
groupList是原始數據聚集,List<T>
sortOrder是排序類型,desc 或許asc
sortName是排序屬性稱號
1.應用反射。
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方法: // 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.挪用AsQueryable()
將泛型 System.Collections.Generic.IEnumerable<T> 轉換為泛型 System.Linq.IQueryable<T>。
var groupQueryList = groupList.AsQueryable();//here var tmpList = groupQueryList.OrderBy(sortName, sortOrder);
須要以下擴大辦法:
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; }
願望本文所述對年夜家的C#法式設計有所贊助。