return 第一组 linq 查询属性作为可选字符串的最简单方法是什么？

Question

将第一组 linq 查询属性作为可选字符串或从类型匿名转换为 (string?, string?) 的最简单方法是什么？由于匿名对象，以下内容不起作用。

private (string? HotemName, string? TransportationName) Get3rdPartyHotelTranporationNames(int customerID, int supplierID, System.DateTime? startDate, System.DateTime? endDate) 
{

    var x = (from res in reservations
             join trans in _unitOfWork.tbl_reservations on res.id_pk equals transRes.id
             where trans.status == 4
             select new
             {
                 HotemName = res.Name,
                 TransportationName = trans.Name
             }).Take(1).Single();

    return x;
}

Answer 1

匿名类型与元组不同。

Anonymous types provide a convenient way to encapsulate a set of read-only properties into a single object without having to explicitly define a type first. The type name is generated by the compiler and is not available at the source code level. The type of each property is inferred by the compiler.

C# tuples are types that you define using a lightweight syntax. The advantages include a simpler syntax, rules for conversions based on number (referred to as cardinality) and types of elements, and consistent rules for copies, equality tests, and assignments. As a tradeoff, tuples do not support some of the object-oriented idioms associated with inheritance.

此外，您不能 return 从函数中输入匿名类型。在您的情况下，您应该 returns 来自 LINQ 的新元组，如下面的代码所示：

private (string? HotemName, string? TransportationName) Get3rdPartyHotelTranporationNames(int customerID, int supplierID, System.DateTime? startDate, System.DateTime? endDate) 
{
    return (from res in reservations
             join trans in _unitOfWork.tbl_reservations on res.id_pk equals transRes.id
             where trans.status == 4
             select (res.Name, trans.Name)
             ).Take(1).Single();
}

return 第一组 linq 查询属性作为可选字符串的最简单方法是什么？

What is the easiest way to return the first set of linq query properties as optional strings?

c#

linq

linq-to-entities