System.InvalidOperationException：LINQ表达式

问题描述

我在webapi（.NET Core 3.1）中设置了一个异步方法，使用linq搜索数据库并获取每个类别的编号，然后将其返回到控制器中。我使用Swagger进行测试，但始终存在错误。我不知道错误在哪里。我可以寻求帮助吗？

服务：

public async Task<ClassficationSimpleInfo[]> SearchZulib(string token,string keyWord)  
{  
    var data = zudb.ZuFileinfo.Include(x => x.Classify).Where(x => x.IsHiden != 1)  
        .Where(x => keyWord == "" || x.FamilyName.Contains(keyWord) || x.Description.Contains(keyWord))  
        .GroupBy(x => x.Classify)  
        .Select(x => new { classify = x.Key,count = x.Count() })  
        .ToList();  
    var result = data.Select(x => new ClassficationSimpleInfo(x.classify.Name,x.classify.ClassificationCode)  
    {  
        Count = x.count,Folder = x.classify.Folder,}).ToArray();  
    return result;  
}

控制器：

        [HttpGet]
        [Route("Controller/SearchZulib")]
        public async Task<ClassficationSimpleInfo[]> SearchZulib(string token,string keyWord)
        {
            return await service.SearchZulib(token,keyWord);
        }  

相关类的定义：

namespace ZulibWebServer.Entities
{
    public class ClassficationSimpleInfo
    {
        public int Id { get; set; }

        public string ClassifyCode { get; set; }

        public string Name { get; set; }

        public int Count { get; set; }

        public string Folder { get; set; }

        public bool Existed { get; set; }

        public ClassficationSimpleInfo(string name,string classifyCode)
        {
            Name = name;
            ClassifyCode = classifyCode;
        }
    }
}
namespace ZulibWebServer.Models
{
    public partial class ZuFileinfo
    {
        public int FileId { get; set; }
        public string FamilyName { get; set; }
        public string FileUrl { get; set; }
        public int ClassifyId { get; set; }
        public string Description { get; set; }
        public byte[] ThumbImage { get; set; }
        public int? MinVer { get; set; }
        public string LargeImage { get; set; }
        public int IsHiden { get; set; }
        public string UploaderName { get; set; }
        public int? UploaderId { get; set; }

        public virtual ZuClassfication Classify { get; set; }
    }
}
public partial class ZuClassfication
    {
        public ZuClassfication()
        {
            ZuFileinfo = new HashSet<ZuFileinfo>();
            ZuMapingrule = new HashSet<ZuMapingrule>();
        }

        public int ClassificationIdid { get; set; }
        public string ClassifyName { get; set; }
        public string ClassificationCode { get; set; }
        public string RelQc { get; set; }
        public string RelCbimcode { get; set; }
        public string RelOminClass { get; set; }
        public string Reluniformat { get; set; }
        public string OtherCode { get; set; }
        public string Name { get; set; }
        public int? ParentCodeId { get; set; }
        public string Folder { get; set; }

        public virtual ICollection<ZuFileinfo> ZuFileinfo { get; set; }
        public virtual ICollection<ZuMapingrule> ZuMapingrule { get; set; }
    }
}

但是错误响应是

system.invalidOperationException：LINQ表达式'DbSet
其中（z => z.IsHiden！= 1） .where（z => False || z.FamilyName.Contains（__ keyWord_0）|| z.Description.Contains（__ keyWord_0））
.Join（外部：DbSet，内部：z => EF.Property>（z，“ ClassifyId”），externalKeySelector：z0 => EF.Property>（z0，“ ClassificationIdid”），innerKeySelector：（o，i）=>新的TransparentIdentifier（外部= o，内部= i）） .GroupBy（来源：z => z.Inner，keySelector：z => z.Outer）'。
以一种可以翻译的形式重写查询，或者通过插入对AsEnumerable（），AsAsyncEnumerable（），ToList（）或ToListAsync（）的调用来显式切换到客户端评估。有关更多信息，请参见https://go.microsoft.com/fwlink/?linkid=2101038。

解决方法

我再次对其进行了测试，并在GroupBy（x => x.Classify）中发现了错误，因此我修改了代码以两次查询数据库。

var data =await zudb.ZuFileinfo
    .Where(x => x.IsHiden != 1)
    .Where(x => keyWord == "" || x.FamilyName.Contains(keyWord) || x.Description.Contains(keyWord))
    .GroupBy(x => x.ClassifyId).Select(x => new { classifyId = x.Key,count = x.Count() })
    .ToListAsync();

var classifies =await zudb.ZuClassfication.ToDictionaryAsync(x => x.ClassificationIdid);

var result = data.Select(x =>
    {
         if (!classifies.TryGetValue(x.classifyId,out var classify)) return null;
         return new ClassficationSimpleInfo(classify.Name,classify.ClassificationCode)
              {
                  Count = x.count,Folder = classify.Folder,};
    }).ToArray();

最后，我成功了。

,

我再次对其进行了测试，发现GroupBy（x => x.Classify）中的错误

是的，通过导航属性进行分组是无效的。

此外，您可以通过linq简化查询，如下所示：

var data = zudb.ZuFileinfo.Include(x => x.Classify).Where(x => x.IsHiden != 1)
    .Where(x => keyWord == "" || x.FamilyName.Contains(keyWord) || x.Description.Contains(keyWord))
    .GroupBy(x => x.ClassifyId)
    .Select(x => new { classifyId = x.Key,count = x.Count() })
    .ToList();

var result = (from d in data
            join c in zudb.ZuClassfication on d.classifyId equals c.ClassificationIdid
            select new ClassficationSimpleInfo(c.Name,c.ClassificationCode)
            {
                Count = d.count,Folder = c.Folder
            }).ToArray();