Question

首先，我的控制器中有一个变量来存储linq查询结果，如下所示：

var test= from m in db.testTable
          join n in db.testTable2
          on m.ID equals n.ID into tabA
          from a in tabA
          join o in db.testTable3
          on m.UserID equals o.ID
          select new { .................};
if (test.Count() > 0)
{
    foreach (var k in test)
    {
        ViewData["dropDown_xxx"] = test.Select(j => new { Value = j.ID, Text = j.Description})
                                   .AsEnumerable()
                                   .Select(j => new SelectListItem // Work with in-memory objects using LINQ to Objects instead of LINQ to Entities
                            {
                                Value = j.Value.ToString(),
                                Text = j.Text
                            }).ToList();
                    }

以上工作完美，我可以生成下拉列表和ViewData 现在我正在尝试将此linQ查询移动到另一个类而不是放入此控制器，如下所示：

public class testClass{
    public IQueryable<dynamic> TestMethod(){
        return from m in db.testTable
        join n in db.testTable2
        on m.ID equals n.ID into tabA
        from a in tabA
        join o in db.testTable3
        on m.UserID equals o.ID
        select new { .................};
    }
}

现在在我之前的Controller中调用它：

       var test= new testClass().TestMethod();
if (test.Count() > 0)
{
    foreach (var k in test)
    {
        ViewData["dropDown_xxx"] = test.Select(j => new { Value = **j.ID**, Text = **j.Description**})
                                   .AsEnumerable()
                                   .Select(j => new SelectListItem // Work with in-memory objects using LINQ to Objects instead of LINQ to Entities
                            {
                                Value = j.Value.ToString(),
                                Text = j.Text
                            }).ToList();
                    }

我可以知道代码有什么问题吗？在 J.ID 和 J.Description ，它现在抱怨表达式树可能不包含动态操作

Answer 1

此处您的动态类型仅在TestMethod的范围内。您最好创建新类并将该类返回给调用者。

public class testClass{
    public IQueryable<MyClass> TestMethod(){
        return from m in db.testTable
        join n in db.testTable2
        on m.ID equals n.ID into tabA
        from a in tabA
        join o in db.testTable3
        on m.UserID equals o.ID
        select new MyClass{ .................};
    }
}

如果您需要返回匿名类型，请检查此

Can't return anonymous type from method? Really?

MVC LinQ IQueryable匿名类型处理

1 个答案: