实体框架核心 Lambda 表达式连接 4 个表并使用 where 进行过滤

Question

I have six tables as shown below. I am trying to get data based on Application_name , Environment_name , and Status .

Status table:

Id, Name

Application table:

Id, Name

Servers table:

Id, ServerName, Status

Environments table:

Id, Name

ResourceGroup table:

Id, Name, Application_Id, Environment_Id

ServersResourceGroup:

Id, Server_Id, Resource_Id

What I am trying to do is join all the require table and use where to filter data by Application_name , Environment_name , and Status

Here is my query I built, which returns all the data back by filtering Application_name but I am no way near to fulfill above requirement by adding additional filters by Environment_name and Status :(

So below is the query that returns all the data with Application_name

public IEnumerable<ResourceGroup> GetAllServersByApplication(string application_name, string environment_name, string status)
{
    var query = _context.ResourceGroup
            .Include(a => a.Application)
            .Include(t => t.Type)
            .Include(e => e.ServersGroup).ThenInclude(e => e.Environment)
            .Include(s => s.ServersGroup).ThenInclude(s => s.Server)
            .Include(s => s.ServersGroup).ThenInclude(s => s.Server).ThenInclude(s => s.Status)
            .Where(a => a.Application.Name == application_name)
            .ToList();

    return query;
}

Here is the query that I am trying to write that will filter based on all three filters:

    public IEnumerable<ResourceGroup> GetAllServersByApplication(string application_name, string environment_name, string status)
    {
        var query = _context.ResourceGroup
            .Include(a => a.Application)
            .Include(t => t.Type)
            .Include(e => e.ServersGroup).ThenInclude(e => e.Environment)
            .Include(s => s.ServersGroup).ThenInclude(s => s.Server)
            .Include(s => s.ServersGroup).ThenInclude(s => s.Server).ThenInclude(s => s.Status)
            .Where(a => a.Application.Name == application_name)
            .Select(e => e.ServersGroup.Where(s => s.Environment.Name == environment_name && s.Server.Status.Name == status)
            .ToList();

        return query;
    }

I get a red line under return query . Please see below image:

Is there any easier way to write lambda query then what I am trying to do?

Any help is really appreciated. :)

Thanks,

Ray

Answer 1

There error is because you are now returning an collection of ServersGroup which is different than in your method signature. This is due to the fact that you added a Select clause and selected property ServersGroup from ResourceGroup . Filtering should happen in the Where clause. I updated the code below and moved your filter in the Select to the Where , also the included where was changed to an Any as a Where expects boolean clauses.

If it was your intention to only include certain ServersGroup within your ResourceGroup then you should filter those out in a join or outer join statement.

Also you probably do not need Include's everywhere. Includes are used for eager loading which ensures that only one roundtrip is necessary to the database to get the associated relationships. If you do not plan on accessing all these related properties then do not include them.

I do assume that your relationships are mapped correctly either in fluent mapping files or using attributes on the models.

public IEnumerable<ResourceGroup> GetAllServersByApplication(string application_name, string environment_name, string status)
{
    var query = _context.ResourceGroup
        .Include(a => a.Application)
        .Include(t => t.Type)
        .Include(e => e.ServersGroup).ThenInclude(e => e.Environment)
        .Include(s => s.ServersGroup).ThenInclude(s => s.Server)
        .Include(s => s.ServersGroup).ThenInclude(s => s.Server).ThenInclude(s => s.Status)
        .Where(a => a.Application.Name == application_name && a.ServersGroup.Any(s => s.Environment.Name == environment_name && s.Server.Status.Name == status))
        .ToList();

    return query;
}