使用LINQ连接两个表并从两个表中获取少量列

Question

public IQueryable GetAllCountry()
{
    using (Context context = new Context())
    {
        var countries = context.COUNTRY.Select(c => new
         {
             country = new
              {
                  ID = c.ID,
                  Description = c.DESCRIPTION,
                  Currency = c.CURRENCY.CURRENCY_SYMBOL,
                  Language = context.LANGUAGE.Select( l => new { lang = l.COUNTRY.CURRENCY_ID})
               }
             });

                return countries;
            }

        }

Above is a LINQ query which fetches results from two tables COUNTRY and LANGUAGE. One COUNTRY can have many LANGUAGE. I want to fetch all the LANGUAGE for a particular COUNTRY. How Can I do it?

When I run my query I get following result:

Argentina  -->System.Collections.Generic.List`1[<>f__AnonymousType0`1[System.Nullable`1[System.Int32]]]
Australia  -->System.Collections.Generic.List`1[<>f__AnonymousType0`1[System.Nullable`1[System.Int32]]]
Bangladesh  -->System.Collections.Generic.List`1[<>f__AnonymousType0`1[System.Nullable`1[System.Int32]]]
Bahrain  -->System.Collections.Generic.List`1[<>f__AnonymousType0`1[System.Nullable`1[System.Int32]]]
Bahamas  -->System.Collections.Generic.List`1[<>f__AnonymousType0`1[System.Nullable`1[System.Int32]]]
Brunei  -->System.Collections.Generic.List`1[<>f__AnonymousType0`1[System.Nullable`1[System.Int32]]]

Answer 1

Your are reading the COUNTRY.CURRENCY_ID from the LANGUAGE table. It doesn't seem that you need that kind of information. If your LANGUAGE and COUNTRY tables have relations, you could have said:

public IQueryable GetAllCountry()
{
    using (Context context = new Context())
    {
        var countries = context.COUNTRY.Select(c => new
        {
            country = new
            {
                ID = c.ID,
                Description = c.DESCRIPTION,
                Currency = c.VFS_CURRENCY.CURRENCY_SYMBOL,
                Language = c.Languages.Select( l => new { l.Description /* desired field from LANGUAGE */ } )
            }
        });
        return countries;
    }
}

Answer 2

I hope it will help you:

 public IQueryable GetAllCountry()
 {
    using (Context context = new Context())
    {
    var countries = context.COUNTRY.Select(c => new
     {
         country = new
          {
              ID = c.ID,
              Description = c.DESCRIPTION,
              Currency = c.VFS_CURRENCY.CURRENCY_SYMBOL,
              List<Language> = context.LANGUAGE.Where( l => l.Currency_ID ==c.COUNTRY.CURRENCY_ID}).ToList()//I just guess your LANGUAGE table has Currency_ID column
           }
         });

            return countries;
        }

    }