无法将匿名类型#1 []隐式转换为匿名类型#2 []

Question

我有以下场景:

public JsonResult ChangeFilterList(int option)
{
    var data = new[] { new { Text = "Unknown option", Value = -1 } };
    switch (option)
    {
        case 2: data = _departmentnameRepository.All.Select(x => new { Text = x.DeptName, Value = x.Id }).ToArray();
            break;
        case 3: data = Session["projectid"] == null
                ? _assetSequenceRepository.All.Select(x => new { Text = x.AssetShotName, Value = x.Id }).ToArray()
                : _assetSequenceRepository.FindBy(p => p.ProjectId == (int)Session["projectid"]).Select(x => new { Text = x.AssetShotName, Value = x.Id }).ToArray();
            break;
        default: data = _userRepository.All.Select(x => new { Text = x.DisplayName, Value = x.UserID }).ToArray();
            break;
    }            

    return Json(data, JsonRequestBehavior.AllowGet);
}

case2并且default看起来很棒但是对案例3(有条件的)抱怨说:Cannot implicitly convert type 'AnonymousType#1[]' to 'AnonymousType#2[]'.不?:应该能够决定类型,因为我已经为匿名提供了蓝图var data = new[] { new { Text = "Unknown option", Value = -1 } };.

解:

@Darin Dimitrov答案很棒,但我希望对匿名类型进行一些测试(简单情况总是需要它).由于犯罪嫌疑人@Douglas:我assetSequenceRepository正提供id的long和匿名的Value推移赞成int不是long.由于C#编译器没有隐式转换long为int,我得到了错误.编译片段是:

public JsonResult ChangeFilterList(int option = 3)
        {
            var data = new[] { new { Text = "Unknown option", Value = long.MaxValue } };
            switch (option)
            {
                case 2: data = _departmentnameRepository.All.Select(x => new { Text = x.DeptName, Value = (long)x.Id }).ToArray();
                    break;
                case 3: data = Session["projectid"] == null
                        ? _assetSequenceRepository.All.Select(x => new { Text = x.AssetShotName, Value = x.Id }).ToArray()
                        : _assetSequenceRepository.FindBy(p => p.ProjectId == (int)Session["projectid"]).Select(x => new { Text = x.AssetShotName, Value = x.Id }).ToArray();
                    break;
                default: data = _userRepository.All.Select(x => new { Text = x.DisplayName, Value = (long)x.UserID }).ToArray();
                    break;
            }            

            return Json(data, JsonRequestBehavior.AllowGet);
        }

Answer 1

您正在将编译器置于此处进行实际测试.只需编写一个视图模型来结束其痛苦并使事情更明确:

public class MyViewModel
{
    public int Value { get; set; }
    public string Text { get; set; }
}

然后将LINQ查询投影到此视图模型,以避免使用条件运算符和匿名类型可能产生的任何歧义:

public ActionResult ChangeFilterList(int option)
{
    var data = new[] 
    { 
        new MyViewModel { Text = "Unknown option", Value = -1 } 
    };

    switch (option)
    {
        case 2: data = _departmentnameRepository
            .All
            .Select(x => new MyViewModel { Text = x.DeptName, Value = x.Id })
            .ToArray();
            break;
        case 3: data = Session["projectid"] == null
                ? _assetSequenceRepository
                    .All
                    .Select(x => new MyViewModel { Text = x.AssetShotName, Value = x.Id })
                    .ToArray()
                : _assetSequenceRepository
                    .FindBy(p => p.ProjectId == (int)Session["projectid"])
                    .Select(x => new MyViewModel { Text = x.AssetShotName, Value = x.Id })
                    .ToArray();
            break;
        default: data = _userRepository
            .All
            .Select(x => new MyViewModel { Text = x.DisplayName, Value = x.UserID })
            .ToArray();
            break;
    }            

    return Json(data, JsonRequestBehavior.AllowGet);
}