'可为空的 object 必须有一个值。' 用于 LINQ c# 中的 ICollection
[英]'Nullable object must have a value.' for ICollection in LINQ c#
问题描述
In my project I am trying to make this Context Object.
在我的项目中，我试图制作这个上下文 Object。
securityContext.Engagement = new EngagementContext(
engagement.EngagementId,
engagement.GUID,
engagement.Name,
null,
engagement.ClientId,
engagement.Client?.GUID ?? Guid.Empty,
engagement.Client?.Name,
null);
That 4th parameter however I dont want always to be null, instead I want it to be null when a userRoleId doesnt exist.但是，我不希望第 4 个参数总是 null，而是当 userRoleId 不存在时，我希望它是 null。 For reference its a IEnumerable Item of type "RoleType" that comes in there when assigning Ive tried replacing that 4th parameter with both of these following lines and keep getting " System.InvalidOperationException: Nullable object must have a value. "作为参考，它在分配时出现了“RoleType”类型的 IEnumerable 项，我尝试用以下两行替换第 4 个参数并继续获取“System.InvalidOperationException：Nullable object 必须有一个值。”
(engagement.EngagementUsers != null ? engagement.EngagementUsers?.Select(X => (RoleType)X?.RoleId) ?? null : null)
and和
engagement.EngagementUsers?.Select(X => (RoleType)X.RoleId) ?? null,
How can I better go about this?我怎样才能更好地解决这个问题？
1 个解决方案
解决方案1
-2 2021-04-30 21:40:58
In my project I am trying to make this Context Object.在我的项目中，我试图制作这个上下文 Object。
securityContext.Engagement = new EngagementContext(
engagement.EngagementId,
engagement.GUID,
engagement.Name,
null,
engagement.ClientId,
engagement.Client?.GUID ?? Guid.Empty,
engagement.Client?.Name,
null);
That 4th parameter however I dont want always to be null, instead I want it to be null when a userRoleId doesnt exist.但是，我不希望第 4 个参数总是 null，而是当 userRoleId 不存在时，我希望它是 null。 For reference its a IEnumerable Item of type "RoleType" that comes in there when assigning Ive tried replacing that 4th parameter with both of these following lines and keep getting " System.InvalidOperationException: Nullable object must have a value. "作为参考，它在分配时出现了“RoleType”类型的 IEnumerable 项，我尝试用以下两行替换第 4 个参数并继续获取“System.InvalidOperationException：Nullable object 必须有一个值。”
(engagement.EngagementUsers != null ? engagement.EngagementUsers?.Select(X => (RoleType)X?.RoleId) ?? null : null)
and和
engagement.EngagementUsers?.Select(X => (RoleType)X.RoleId) ?? null,
How can I better go about this?我怎样才能更好地解决这个问题？
声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.