Question

我在foreach循环中指向in时出错！？从来没有发生过。这可能是什么原因？我错过了什么吗？

错误讯息：

类型＆＃39; System.NotSupportedException＆＃39;的例外情况发生在EntityFramework.SqlServer.dll中但未在用户代码中处理

其他信息：无法创建常量类型的值＆＃39; System.Object＆＃39;。只有原始类型或者在此上下文中支持枚举类型。

我的代码：

List<int> WeeksInProject = new List<int>();
var w = from x in db.Activities 
        where x.ProjectID.Equals(1) 
        select x;

foreach (var wNum in w)
{
    WeeksInProject.Add(wNum.WeekNumber);
}

Answer 1

<button class='addNew'>
        <i class="fa fa-plus" ></i> Add new 
        <span style='text-decoration:underline'>Object</span>
</button>

应该是：

var w = from x in db.Activities 
        where x.ProjectID.Equals(1) select x;

如果var w = from x in db.Activities where x.ProjectID == 1 select x;是ProjectID，

int?

Answer 2

List<int> WeeksInProject = new List<int>();
var w = from x in db.Activities 
        where x.ProjectID != null && (int)x.ProjectID == 1 
        select x;

foreach (var wNum in w)
{
    WeeksInProject.Add(wNum.WeekNumber);
}

由于ProjectID是int?，您必须检查无效然后投射它。

Foreach循环错误

2 个答案: