构建谓词时，请将
我想从数据库下载过滤后的数据。
在这里它过滤数据
return predicate
.And(true, () => company => !String.IsNullOrEmpty(searchCriteria.Keyword) ? searchCriteria.Keyword.Contains(company.Name) : true)
.Or(true, () => company => !String.IsNullOrEmpty(searchCriteria.Keyword) ? company.Employees.Any(x => x.FirstName == searchCriteria.Keyword) : true)
.Or(true, () => company => !String.IsNullOrEmpty(searchCriteria.Keyword) ? company.Employees.Any(x => x.LastName == searchCriteria.Keyword) : true)
.And(true, () => company => searchCriteria.EmployeeDateOfBirthFrom != null ? company.Employees.Any(x => x.DateOfBirth >= searchCriteria.EmployeeDateOfBirthFrom) : true)
.And(true, () => company => searchCriteria.EmployeeDateOfBirthTo != null ? company.Employees.Any(x => x.DateOfBirth <= searchCriteria.EmployeeDateOfBirthTo) : true)
.And(true, () => company => searchCriteria.EmployeeJobTitles != null ? company.Employees.Any(x=> searchCriteria.EmployeeJobTitles.Any(s=> s == x.JobTitle.ToString())) : true);
我在这里从数据库下载数据：
return await dbContext.Companies.Include(x => x.Employees).Where(predicate).ToListAsync();
为什么我有这个问题，我能解决吗？
System.InvalidOperationException: The LINQ expression 'DbSet<Employee>
.Where(e => EF.Property<Nullable<long>>((EntityShaperExpression:
EntityType: Company
ValueBufferExpression:
(ProjectionBindingExpression: EmptyProjectionMember)
IsNullable: False
), "Id") != null && EF.Property<Nullable<long>>((EntityShaperExpression:
EntityType: Company
ValueBufferExpression:
(ProjectionBindingExpression: EmptyProjectionMember)
IsNullable: False
), "Id") == EF.Property<Nullable<long>>(e, "CompanyId"))
.Any(e => __searchCriteria_EmployeeJobTitles_0
.Contains(e.ToString()))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync(). See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.
at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.<VisitMethodCall>g__CheckTranslated|8_0(ShapedQueryExpression translated, <>c__DisplayClass8_0& )
EF Core无法翻译以下表达式：
company.Employees.Any(x => searchCriteria.EmployeeJobTitles
.Any(s => s == x.JobTitle.ToString()))
它有两个问题。
首先，searchCriteria.EmployeeJobTitles似乎在内存集合中，而内存集合中当前唯一可翻译的运算符是Contains。
所以应该改为
company.Employees.Any(x => searchCriteria.EmployeeJobTitles
.Contains(x.JobTitle.ToString()))
但根据异常消息，你已经这么做了。这就引出了第二个问题：x.JobTitle属性类型似乎是enum，而enum的ToString()无法转换。
因此，您必须以其他方式执行枚举过滤器-将searchCriteria.EmployeeJobTitles从IEnumerable<string>转换为IEnumerable<JobTitle>并使用Contains(x.JobTitle)，这样可以避免x.JobTitle.ToString():
company.Employees.Any(x => searchCriteria.EmployeeJobTitles
.Select(t => Enum.Parse<JobTitle>(t))
.Contains(x.JobTitle))
x.JobTitle.ToString()更改为x.JobTitle。数据库端不支持ToString()。