初始化 classObject = new(); 时出现编译错误

Question

在我们的 .NET REST-API 中，我有一个 DTO 类和一个 C# 控制器类。 DTO 类如下，没有任何编译错误。 该 DTO 包含一个用于检查的变量和一个用于检查期间观察到的缺陷列表的 IEnumerable/list-variable。当没有缺陷时，“列表”可能为空。这类似于添加具有多个发票项目的发票的排列。

public class PTInspectionAndTMDefectsDTO {

public required PTINSPECTION PtInspection { get; set; }
public IEnumerable<TMDEFECT> TMDefects { get; set; } = Enumerable.Empty<TMDEFECT>();

// Constructors.
public PTInspectionAndTMDefectsDTO(PTINSPECTION ptinspection) { PtInspection = ptinspection; }
public PTInspectionAndTMDefectsDTO(PTINSPECTION ptinspection, IEnumerable<TMDEFECT> tmdefects) { PtInspection = ptinspection; TMDefects = tmdefects; }
}

这是控制器功能代码，我使用提供所需 PTInspection 变量的第一个构造函数来初始化

PTInspectionAndTMDefectsDTO createdInspectionAndDefects

。最后一个 C# 语句中出现编译错误。

[HttpPost("AddPTInspectionAndDefects")]
public async Task<IActionResult> AddPTInspectionAndDefects([FromBody] PTInspectionAndTMDefectsDTO oDataToAdd) {
    PTINSPECTION addThisInspection = oDataToAdd.PtInspection;
    IEnumerable<TMDEFECT>? addTheseDefects = oDataToAdd.TMDefects;
    PTINSPECTION createdInspection = new PTINSPECTION();
    TMDEFECT? createdDefect = new TMDEFECT();
    IEnumerable<TMDEFECT> createdDefectList = Enumerable.Empty<TMDEFECT>();
    PTInspectionAndTMDefectsDTO createdInspectionAndDefects = new(createdInspection); 
... a compilation error appears for the above sentence with a red-squiggle under the word [new] -- see image below.
... other code is not provided...

错误CS9035没有更多信息。 我不确定为什么

new(createdInspection);

无效。欢迎您的帮助。谢谢...约翰

Answer 1

您需要用

SetsRequiredMembersAttribute

标记演员。

否则，您必须在对象初始值设定项中设置

required

属性。

using System.Diagnostics.CodeAnalysis;

public class PTInspectionAndTMDefectsDTO
{
    public required PTINSPECTION PtInspection { get; set; }

    public IEnumerable<TMDEFECT> TMDefects { get; set; } = Enumerable.Empty<TMDEFECT>();

    // Constructors.
    [SetsRequiredMembers]
    public PTInspectionAndTMDefectsDTO(PTINSPECTION ptinspection)
    {
        PtInspection = ptinspection;
    }

    [SetsRequiredMembers]
    public PTInspectionAndTMDefectsDTO(PTINSPECTION ptinspection, IEnumerable<TMDEFECT> tmdefects)
    {
        PtInspection = ptinspection;
        TMDefects = tmdefects;
    }
}