Question

我有一个FileInfo列表，我必须按不同的属性排序，例如

List<FileInfo> infoListOrdered = infoList.OrderBy(x => x.CreationTime).ToList();

不是为每个FileInfo属性编写表达式，而是可以将TKey作为参数传递吗？

Answer 1

不，TKey是一种类型; lamba x=>x.CreationTime是值选择器，返回类型TKey的值。您不能仅根据其类型选择某些内容，因为您的类中可能有多个该类型的属性实例。

Answer 2

这是基于我（错误）理解问题的解决方案。它为您可能想要订购的每个属性OrderBy提供prop：

static void Main()
{
    IEnumerable<FileInfo> infoList = XXX; // your source to sort

    var orderByMeth = typeof(Enumerable).GetMethods().Single(m => m.Name == "OrderBy" && m.GetParameters().Length == 2);
    var tFileInfo = typeof(FileInfo);
    foreach (var prop in tFileInfo.GetProperties(BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.Instance))
    {
        var tKey = prop.PropertyType;

        var xParam = Expression.Parameter(tFileInfo);
        var propBody = Expression.Property(xParam, prop.GetMethod);
        var lambda = Expression.Lambda(propBody, xParam);
        var func = lambda.Compile();

        var orderByMethConstr = orderByMeth.MakeGenericMethod(tFileInfo, tKey);

        var result = orderByMethConstr.Invoke(null, new object[] { infoList, func, });
        var infoListOrdered = (IOrderedEnumerable<FileInfo>)result;

        // keep infoListOrdered; foreach through it to get that particular ordering
    }
}

OrderBy与变量TKey

2 个答案: