声明并初始化用于分配匿名类型列表的变量

Question

我尝试加入两个表：

var data = from request in context.Requests
                        join account in context.AutolineAccts
                            on request.PkRequest.ToString() equals account.AccountCode
                        select new 
                        {
                            ID = request.PkRequest.ToString(),
                            Location = request.FkLocation,
                            RequestDate = request.RequestDate.Value,
                            Requestor = request.FkRequestor,
                            DebitorNr = request.FkDebitor.ToString(),
                            NewDebit = request.Debit.ToString(),
                            ApprovalStatus = request.ApprovalStatus.ToString(),
                            RecommendationStatus = request.RecommendationStatus.ToString(),
                            DebitorName = account.CustomerSname,
                            Limit = account.CreditLimit
                        };

现在我想根据用户的状态过滤结果集：

// Accounting user
if (ActiveDirectoryHelper.CheckIfUserIsInADGroup(userLogin, AdGroups.ACCOUNTING) )

    req = data.Where(x => x.RecommendationStatus == null).ToList();

// After sales manager
else if (ActiveDirectoryHelper.CheckIfUserIsInADGroup(userLogin, AdGroups.SAV_LEADERS))
    req = data.OrderByDescending(x => x.ID).ToList();

// Everybody else
else 
    req = data.OrderByDescending(x => x.PkRequest).ToList();

这就是我卡住的地方。当我没有加入并且只检索“请求”类型时，我可以声明一个请求列表

List<Requests> req;

但是对于 Requests 和 AutolineAccts 的组合，我必须声明并初始化一个“项目”（req）列表，以将结果集分配给 if-else 段。但我不知道那个匿名变量应该是什么样子。

稍后我必须将结果集映射到我的 IndexViewModels 列表：

foreach (var item in req)
                viewModel.CLModels.Add(new IndexViewModel
                {
                    ID = item .PkRequest.ToString(),
                    Location = item .FkLocation,
                    RequestDate = item .RequestDate.Value,
                    Requestor = item .FkRequestor,
                    DebitorNr = item .FkDebitor.ToString(),
                    NewDebit = item .Debit.ToString(),
                    ApprovalStatus = item .ApprovalStatus.ToString(),
                    RecommendationStatus = item .RecommendationStatus.ToString(),
                    DebitorName = item.CustomerSname,
                    Limit = item.CreditLimit
                });

有解决这个问题的办法吗？

Answer 1

IEnumerable<dynamic> result = from request in requests
                    join account in accounts
                        on request.id equals account.id
                        select new {id=request.id, name=account.name};

保留访问器，可以进一步查询，是方法的返回类型。

Answer 2

避免dynamic 的一个选择是给编译器一个你的匿名类型的例子：

var req = new[]
{
    new
    {
        ID = "",
        Location = "",
        RequestDate = DateTime.Now,
        Requestor = "",
        DebitorNr = "",
        NewDebit = "",
        ApprovalStatus = "",
        RecommendationStatus = "",
        DebitorName = "",
        Limit = 0
    }
}.ToList();

显然您应该调整值以匹配您期望的类型。

这有点难看，但我个人更喜欢使用动态类型。

如果你想避免实际分配数组和列表，你可以以一种相当可怕的方式使用类型推断：

// Simple method that returns null, but enables type inference
public static List<T> ProvideNullList(T sample) => null;

// Call it when you want to declare your variable:
var sample = new
{
    ID = "",
    Location = "",
    RequestDate = DateTime.Now,
    Requestor = "",
    DebitorNr = "",
    NewDebit = "",
    ApprovalStatus = "",
    RecommendationStatus = "",
    DebitorName = "",
    Limit = 0
};
var req = GenericHelpers.ProvideNullList(sample);

这仍然会分配样本，但它至少比数组和列表好位。