C# EF核心NullReferenceException访问相关实体

如何使用Lambda EF core更新子表值

var UpdatePercentage = _context.TaskOverview.Single(c => c.Id == 100);
UpdatePercentage.Completedpercentage = 30;
UpdatePercentage.TaskSubInfo.Content1 = "Some value";

await _context.SaveChangesAsync();

我得到NullReferenceException错误

NullReferenceException: Object reference not set to an instance of an object.

你可以用

---

我猜您在相关的

实体

TaskSubInfo上得到了

NullReferenceException

EntityFramework

默认情况下不加载相关的

实体，但

var UpdatePercentage = _context.TaskOverview
                            .Include(to => to.TaskSubInfo)
                            .Single(c => c.Id == 100);

UpdatePercentage?.Completedpercentage = 30;
UpdatePercentage?.TaskSubInfo.Content1 = "Some value";

await _context.SaveChangesAsync(); 

您在三行中的哪一行得到异常：您的_上下文是否为空？或者UpdatePercentage.CompletedPercentage为空？或者UpdatePercentage.TaskSubInfo为空？可能是的重复项
var UpdatePercentage = _context.TaskOverview
                            .Include(to => to.TaskSubInfo)
                            .Single(c => c.Id == 100);

UpdatePercentage?.Completedpercentage = 30;
UpdatePercentage?.TaskSubInfo.Content1 = "Some value";

await _context.SaveChangesAsync();