使用实体框架根据过滤器（非必填字段）获取数据

Question

我需要从名为Student 的实体中获取数据，该实体具有字段（Id、Name、Age、Dob）。我有一个请求对象StudentFilter

public class StudentFilter 
{
      public int? Id {get;set;}
      public string Name {get;set;}
      public int Age {get;set;}
      public DateTime Dob {get;set;}
}

现在基于此，我需要使用这些过滤器形成一个查询并从数据库中获取数据：

public List<Student> Get(StudentFilter  request)
{
     if(request.Id.HasValue && request.Id > 0)
     {
     }

     if(request.Age.HasValue && request.Age > 0)
     {
     }

     if(request.Dob.HasValue)
     {
     }

     _context.<Student>.Get()
}

有人可以帮我吗？在此先感谢

Answer 1

试试这个，根据你的情况链接.Where

var query = context.Students.AsQueryable();

if(request.Id.HasValue && request.Id > 0)
{
    //equal query
    query = query.Where(x => x.Id == request.Id.Value);
    /* greater than or less than and equal to query
    *query = query.Where(x => x.Id >= request.Id.Value) or query.Where(x => x.Id <= request.Id.Value) or query.Where(x => x.Id != request.Id.Value)
    */
}

if(request.Age.HasValue && request.Age > 0)
{
    query = query.Where(x => x.Id == request.Age.Value);
    //same applies to top depending on your condition, can be !=, <=, >= or between (< && >)
}

if(request.Dob.HasValue)
{
    query = query.Where(x => x.Id == request.Dob.Value);
    //same applies to top depending on your condition, can be !=, <=, >=
}

//the ONLY part which the query will be executed
var result = query.ToList();