Question

MVC5 / EF 6

在我看来

@Html.DropDownList("selectPlayer", (SelectList)ViewBag.Players, "Select Player", new { @class = "form-control" })

在我的控制器中：

if (Convert.ToInt32(mySession.Format) == 4)
{
    List<Int32> teamDrawPIDs = new List<Int32>();
    List<TeamDraw> teamDrawPlayers;
    teamDrawPlayers = entityDB.TeamDraws.Where(t => t.TID == TID).ToList();

    foreach (TeamDraw tPlayer in teamDrawPlayers)
    {
        teamDrawPIDs.Add(tPlayer.PID);
    }

    // only get players in TeamDraw
    ViewBag.Players = new SelectList(entityDB.Players.Where(t => (teamDrawPIDs.IndexOf(t.PID) != -1)).OrderBy(p => p.Last), "PID", "selectListName");
}
else
{
    ViewBag.Players = new SelectList(entityDB.Players.OrderBy(p => p.Last), "PID", "selectListName");
}

当mySession.Format不是4时，这一切都正常。但是只要它是4，我的ViewBag.Players仅从ID中的teamDrawPIDs创建，我得到此错误（在视图页面上，控制器很好）：< / p>

＆＃34; LINQ to Entities无法识别方法＆＃39; Int32 IndexOf（Int32）＆＃39;＆＃34;

Answer 1

根据错误，使用IndexOf()的表达式无法转换为Sql。您可以尝试更多Sql Friendly，例如：

entityDB.Players.Where(t => teamDrawPIDs.Contains(t.PID))
                .OrderBy(p => p.Last)

你也可以使用一些linq消除for-each，例如一步到位：

var teamDrawPIDs = teamDrawPlayers.Select(tp => tp.PID).ToList();

Answer 2

实体Frameworrk不支持直接强制转换。所以在我的个人建议设置变量时，我们将使用过滤器以防止此类问题。

LINQ to Entities无法识别方法＆＃39; Int32 IndexOf（Int32）＆＃39;

2 个答案: