如何在拆分后使用 entity framework 搜索文本？

Question

我有一个实体模型

public class User{
   public string FirstName {get;set;}
   public string LastName {get;set;}
   public string Department {get;set;}
}

所以我想使用 entity framework 核心 3.1 在数据库中搜索像 "john smith" 这样的文本。

我之前在拆分正文

    public async Task<IEnumerable<UserListViewModel>> Search(string search)
    {
        var terms = search.Split(" ");

        var queryable = _context.Users.Where(s => terms.All(m => s.Department.ToLower().Contains(m)) ||
                                                  terms.All(m => s.FirstName.ToLower().Contains(m)) ||
                                                  terms.All(m => s.LastName.ToLower().Contains(m))).AsQueryable();

        ...........
        ...........
        ...........
    }

但是不行。

那我该怎么做呢？

Answer 1

我认为你不需要 terms.All。因为“john smith”是一个全名 all，所以不会在名字或姓氏字段中找到它。

我不确定以下是否可行。

var queryable = _context.Users.Where(s => terms.Contains(m => s.Department.ToLower().Contains(m)) &&
                                                  terms.Contains(m => s.FirstName.ToLower().Contains(m)) ||
                                                  terms.All(m => s.LastName.ToLower().Contains(m))).AsQueryable();

虽然不太准确，但return“john john”也是这样，但这种情况很少见。

Answer 2

下面的怎么样

  void Main()
  {
    var users = new List<User>
    {
        new User { FirstName = "John", LastName = "Smith", Department = "Web" },
        new User { FirstName = "Aaliyah", LastName = "Lin", Department = "Warehouse" },
        new User { FirstName = "Cristian", LastName = "Stone", Department = "Cleaning" },
        new User { FirstName = "Kierra", LastName = "Davidson", Department = "Mobile" },
        new User { FirstName = "Lizbeth", LastName = "Gregory", Department = "Web" }
    };
    
    var search = "Lizbeth Gregory";
    var terms = search.ToLower().Split(' ');
    users.Where(s => terms.All(m => s.Department.ToLower().Contains(m)) ||
                                                      (terms.Any(m => s.FirstName.ToLower().Contains(m))) ||
                                                      terms.Any(m => s.LastName.ToLower().Contains(m)))
                                                      .Dump();
}

public class User
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Department { get; set; }
}

Answer 3

EF Core 3.x 在大多数情况下并不真正支持 All 和 Any 的翻译，并且您的代码略有错误，我认为您真正想要的是：

var queryable = _context.Users.Where(u => terms.All(m => u.Department.Contains(m) ||
                                                         u.FirstName.Contains(m) ||
                                                         u.LastName.Contains(m)));

由于无法翻译，您需要将其重新格式化为可以翻译的代码。

使用 LINQKit，您可以使用 PredicateBuilder 创建一个扩展，将查询重新映射到每个术语的一系列 && 测试中：

// searchTerms - IEnumerable<TKey> where all must be in a row's key
// testFne(row,searchTerm) - test one of searchTerms against a row
// dbq.Where(r => searchTerms.All(s => testFne(r,s)))
public static IQueryable<T> WhereAll<T,TKey>(this IQueryable<T> dbq, IEnumerable<TKey> searchTerms, Expression<Func<T, TKey, bool>> testFne) {
    var pred = PredicateBuilder.New<T>();
    foreach (var s in searchTerms)
        pred = pred.And(r => testFne.Invoke(r, s));

    return dbq.Where((Expression<Func<T,bool>>)pred.Expand());
}

你会像这样使用：

var queryable = _context.Users
                    .WhereAll(terms,
                              (u,m) => u.Department.Contains(m) ||
                                       u.FirstName.Contains(m) ||
                                       u.LastName.Contains(m));

对于“john smith”，扩展方法将创建等效于：

var queryable = _context.Users
                    .Where(u => (u.Department.Contains("john") ||
                                 u.FirstName.Contains("john") ||
                                 u.LastName.Contains("john")) &&
                                (u.Department.Contains("smith") ||
                                 u.FirstName.Contains("smith") ||
                                 u.LastName.Contains("smith"))
                           );

Answer 4

另一种解决方案是汇总您的搜索词：

var terms = search
    .Split(' ', StringSplitOptions.RemoveEmptyEntries);
query = terms
    .Aggregate(query, (current, term) =>
         current.Where(x =>
             x.FirstName.Contains(term)
             || x.LastName.Contains(term)
             || x.Department.Contains(term)
         )
    );

如何在拆分后使用 entity framework 搜索文本？

How to search a text using entity framework after split?

c#

linq

entity-framework

entity-framework-core

entity-framework-core-3.1