使用linq从链接到另一个表的表中获取一条记录

Question

The question is confusing since I really didn't know how to ask this.

Anyhow, I have 4 tables and I need to get to the TokenSetting table to get a single record. I am given the companycode and I have to travel from there and get the rest of the information that I need. And because there are multiple corporationstructures to each corporation I have to get the corporationstructure first to get the tokens assigned to it.

Here is the layout:

This is my code:

  _currentcorp = (from c in _entities.Corporations
              where c.CompanyCode == textBox_CompanyCode.Text
              select c).FirstOrDefault();

  if (_currentcorp == null)
  {
    errorProvider1.SetError(textBox_CompanyCode, "Invalid corporation.");
    return;
  }

  var corpstructure = (from cs in _currentcorp.CorporationStructures
                          where cs.District == null &&
                                cs.Branch == null &&
                                cs.Region == null
                          select cs).FirstOrDefault();

  if (corpstructure == null)
  {
    errorProvider1.SetError(textBox_CompanyCode, "Invalid corporation structure.");
    return;
  }

  var tokensetting = (from ts in _currentcorp.Tokens
                      where ts.CorporationStructureId == corpstructure.CorporationStructureId                           
                      select ts.TokenSettings).FirstOrDefault();

tokensetting is coming back as ienumerable even though I'm telling it to get firstordefault. I'm assuming that it's saying get firstordefault on the tokens?

Anyhow, there should only be 1 record in the tokensetting table even though the table is 1 to many. How do I return the firstordefault only on this table?

==== ANSWER ====

As suggested, I did the following:

  var tokensetting = (from ts in _currentcorp.Tokens
                      where ts.CorporationStructureId == corpstructure.CorporationStructureId                           
                      select ts.TokenSettings.FirstOrDefault()).FirstOrDefault();

Answer 1

I believe the LINQ query is returning a IEnumerable of IEnumerables , so a second .FirstOrDefault() should get you what you want.

The first call specifies that you want the first row in the result of the LINQ query, and the second specifies that you want the first element of ts.TokenSettings , which is itself a collection.