使用LINQ連接兩個表並從兩個表中獲取少量列

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;
            }

        }

上面是一個LINQ查詢，它從兩個表COUNTRY和LANGUAGE中獲取結果。 一個國家/地區可以有多種語言。 我想獲取特定國家/地區的所有語言。 我該怎么做？

當我運行查詢時，我得到以下結果：

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

您正在從LANGUAGE表中讀取COUNTRY.CURRENCY_ID 。 似乎您不需要這種信息。 如果您的LANGUAGE和COUNTRY表具有關系，則您可能會說：

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

希望對您有幫助：

 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;
        }

    }