查询多对多和有条件的地方 [英] Querying Many to Many and Conditional Where

问题描述

 保护覆盖在我的上下文文件中，我设置了我的位置类和程序类之间的许多关系。 void OnModelCreating（DbModelBuilder modelBuilder）
 {
 
 modelBuilder.Entity< Location>（）
 .HasMany（u => u.Programs）
 .WithMany（r => r.Locations）
 .Map（m => 
 {
 m.ToTable（LocationsPrograms）; 
 m.MapLeftKey（LocationId）; 
 m.MapRightKey（ProgramId）; 
}）; 
 
} 
  

我正在创建一个搜索/过滤器表单，用户需要通过选择一个程序来过滤这些位置。

我的想法是查询连接点（M2M）表，然后将其备份到位置表

问题是我没有代表M2M表的类，而不是在我的OnModelCreating方法中。

我可以找到一个如何做到这一点的例子吗？

基本上选择*从位置l加入位置程序lp在l.LocationId = lp.locationid和lp.programid =传入的东西。

谢谢。

解决方案

  var locations = dbContext.Locations 
 .Where（l => l.Programs.Any（p => p.ProgramId == whateverWasPassedInId））
 .ToList（）; 
  

或（因为您的主键属性程序）：

  var locations = dbContext.Programs 
 .Where（p => p .ProgramId == whateverWasPassedInId）
 .Select（p => p.Locations）
 .SingleOrDefault（）; 
  

Within my Context file, I set up a many to many relationship between my Location class and Program class.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {

            modelBuilder.Entity<Location>()
            .HasMany(u => u.Programs)
            .WithMany(r => r.Locations)
            .Map(m =>
            {
                m.ToTable("LocationsPrograms");
                m.MapLeftKey("LocationId");
                m.MapRightKey("ProgramId");
            });

        }

I'm creating a search/filter form where the user will need to be able to filter the locations by selecting a program.

My thought was to query the junction (M2M) table and then join that back up with the locations table.

The problem is that I don't have a class representing the M2M table other than in my OnModelCreating method.

Can I get an example on how to do this?

Basically select * from locations l join locationsprograms lp on l.LocationId = lp.locationid and lp.programid = whatever was passed in.

Thank you.

解决方案

var locations = dbContext.Locations
    .Where(l => l.Programs.Any(p => p.ProgramId == whateverWasPassedInId))
    .ToList();

Or (works because your are filtering by the primary key property of Program):

var locations = dbContext.Programs
    .Where(p => p.ProgramId == whateverWasPassedInId)
    .Select(p => p.Locations)
    .SingleOrDefault();

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