c# - 试图从数据库中删除所有匹配的东西，而不仅仅是 firstordefault

Question

这段代码有效，但它只删除了数据库中的第一个位置。我是 .Net 框架的新手。我知道我正在使用 FirstOrDefault；我不知道如何搜索数据库并删除所有符合要求的实例

MMLeagueParticipant removeThisParticipant = db.ParticipatingKids.FirstOrDefault(i=>i.ParticipantId == ParticipantId && i.sport.sport == SportsTab);
if(removeThisParticipant == null)
{
    Console.WriteLine("removeThisParticopant in [IActionResults Remove] was null");
    return RedirectToAction("Dashboard","Dashboard");
}
if(removeThisParticipant != null)
{
    Console.WriteLine("removeThisParticopant in [IActionResults Remove] was NOT null");
    db.ParticipatingKids.Remove(removeThisParticipant);
    db.SaveChanges();
    return RedirectToAction("Dashboard", "Dashboard");
}

我想做什么:

我想删除数据库中满足条件的所有实例。

我尝试了什么:

• .Where() Cannot implicitly convert type 'System.Linq.IQueryable<LeagueProject.Models.MMLeagueParticipant>' to 'LeagueProject.Models.MMLeagueParticipant'.

• .全部()。但这返回一个 bool 值

• .Contains()。还返回了一个 bool 值

Answer 1

您可以使用 Where 而不是 FirstOrDefault 和 Count() 来检查集合

例子:

IEnumerable<MMLeagueParticipant> removeThisParticipant = db.ParticipatingKids.Where(i=>i.ParticipantId == ParticipantId && i.sport.sport == SportsTab);
if (removeThisParticipant.Count() != 0)
{
     Console.WriteLine("removeThisParticopant in [IActionResults Remove] was NOT null");
     db.ParticipatingKids.RemoveRange(removeThisParticipant);
     db.SaveChanges();
     return RedirectToAction("Dashboard", "Dashboard");   
}
else 
{
    Console.WriteLine("removeThisParticopant in [IActionResults Remove] was null");
    return RedirectToAction("Dashboard","Dashboard");
}