Question

我目前正在搜索搜索页面。我只需返回包含存储在int [] ST中的所有主题标签id的主题的主题细节列表。目前该行（ST == null？true：ST.Contains（b.ThemeTagID））似乎给我一个错误

其他信息：无法创建类型为System.Int32 []＆＃39;的null常量值。在此上下文中仅支持实体类型，枚举类型或基元类型。

    public ActionResult Index(int ProviderID = 0, string Description = null, int[] ST = null)
    {

        var themedetail = from t in db.ThemeDetail
                          from b in t.ThemeTags
                          where (
                          (string.IsNullOrEmpty(Description) ? true : t.Description.ToLower().Contains(Description.ToLower())) &&
                          (ProviderID == 0 ? true : t.ProviderID == ProviderID) &&
                          (ST == null ? true : ST.Contains(b.ThemeTagID))
                              )
                          select t;

        ViewBag.ProviderID = new SelectList(db.ProviderDetails, "ProviderID", "ProviderName");
        ViewBag.MultiselectFeatures = new MultiSelectList(db.ThemeFeatures, "ThemeFeatureID", "ThemeFeaturesName");
        ViewBag.MultiselectTags = new MultiSelectList(db.ThemeTags, "ThemeTagID", "TagName");

        return View(themedetail.ToList());
    }

模特是......

[Table("ThemeDetail")]
public class ThemeDetail : Entity
{
    [Required]
    [Display(Name = "Name")]
    public string ThemeName { get; set; }
    public ThemeDetail()
    {
        ThemeFeatures = new List<ThemeFeature>();
        ThemeTags = new List<ThemeTag>();
        ThemeImages = new List<ThemeImage>();
    }

    public virtual ICollection<ThemeFeature> ThemeFeatures { get; set; }
    public virtual ICollection<ThemeTag> ThemeTags { get; set; }
    public virtual ICollection<ThemeImage> ThemeImages { get; set; }
}

[Table("ThemeTags")]
public class ThemeTag
{
    [Key]
    [Display(Name = "Theme Tag ID")]
    public int ThemeTagID { get; set; }

    [Display(Name = "Tag Name")]
    [Required]
    public string TagName { get; set; }

    public virtual ICollection<ThemeDetail> ThemeDetail { get; set; }
}

Answer 1

您在查询中使用了ST，但它无法转换为SQL，因为ST是int[]并且可以是null）而在SQL中没有＆{＆} ＃39; array 的任何概念。

如果您更改查询以避免null检查，则EF可以使用WHERE ThemeTagID IN (...)使用列表中提供的值翻译该查询（如果列表可能来自包含数千个元素的其他查询，请小心）：

public ActionResult Index(int ProviderID = 0...
{
    if (ST == null)
        ST = new int[0];

然后只需更改：

(ST == null ? true : ST.Contains(b.ThemeTagID))

对此：

ST.Contains(b.ThemeTagID)

在此上下文中仅支持实体类型，枚举类型或基元类型

1 个答案: