c# - 在 Entity Framework 查询中使用 Func<>

Question

我有以下 Entity Framework 查询:

Func<Company, bool> filter;
if (officeId != 0)
    filter = company => !company.IsDeleted && company.OfficeCompanies.Any(c => c.OfficeId == officeId);
else
    filter = company => !company.IsDeleted;

var companies = from c in Repository.Query<Company>()
                where filter(c) &&
                    (relationshipTypes.Count() == 0 || relationshipTypes.Any(r => r == c.TypeEnumIndex)) &&
                    c.Description.Contains(term)
                orderby c.Description
                select new JqueryUiAutoCompleteItem
                {
                    label = c.Description,
                    value = SqlFunctions.StringConvert((double)c.Id)
                };

它给我错误:

The LINQ expression node type 'Invoke' is not supported in LINQ to Entities.

如果我删除查询主体中对 filter() 的引用，则不会出现错误。

我理解这个错误的意思:我正在使用无法转换成SQL的代码。但是我的 filter() 有什么不能转换成 SQL 的？

Answer 1

您需要将 Func 切换为 Expression，然后将该表达式直接传递给 LINQ fluent 语法中的 Where。我认为没有办法在查询语法中使用表达式。

Expression<Func<Company, bool>> filter; //<-- changed type
if (officeId != 0)
    filter = company => !company.IsDeleted && company.OfficeCompanies.Any(c => c.OfficeId == officeId);
else
    filter = company => !company.IsDeleted;

var companies = from c in Repository.Query<Company>().Where(filter) // <-- changed syntax
                where (relationshipTypes.Count() == 0 || relationshipTypes.Any(r => r == c.TypeEnumIndex)) &&
                    c.Description.Contains(term)
                orderby c.Description
                select new JqueryUiAutoCompleteItem
                {
                    label = c.Description,
                    value = SqlFunctions.StringConvert((double)c.Id)
                };