C# 使用LINQ到SQL的子查询

我在我的C#教程项目中使用LINQtoSQL，但我有它的基本知识

我进行了如下SQL查询：

SELECT ID,HeroName,HeroRarity,Initiative,Attack,Attack1 
FROM   CharactersName
WHERE  ID IN(
             SELECT HeroID 
             FROM   Hero_Group 
             WHERE GroupID=1
            )

void FilterGroup()
    {
        HDAEntities db = new HDAEntities();
        var query = from obj in db.CharactersNames
                    where obj.ID == from obj2 in db.Hero_Group
                                    where obj2.GroupID == comboBox1.SelectedIndex
                                    select new
                                    {
                                        obj2.GroupID
                                    }
                    select new
                    {
                        obj.ID,
                        obj.HeroName,
                        obj.HeroRarity,
                        obj.Initiative,
                        obj.Attack,
                        obj.Attack1
                    };
    }

void FilterGroup()
{
    HDAEntities db = new HDAEntities();

    var subQuery = db.Hero_Group.Where(h => h.GroupID == comboBox1.selectedIndex)
                                .Select(h => h.GroupID);

    var query = from obj in db.CharactersNames
                where subQuery.Contains(obj.ID)
                select new
                {
                    obj.ID,
                    obj.HeroName,
                    obj.HeroRarity,
                    obj.Initiative,
                    obj.Attack,
                    obj.Attack1
                };

    var result = query.ToList(); // this is where your query and subquery are evaluated and sent to the database

    db.Dispose();
    db = null;
}

（Hero_Group）是一个表，用于处理（CharactersName）表和另一个名为（Groups）的表之间的多对多关系，其中一个字符可以位于多个组中

我试着用LINQ这样写：

SELECT ID,HeroName,HeroRarity,Initiative,Attack,Attack1 
FROM   CharactersName
WHERE  ID IN(
             SELECT HeroID 
             FROM   Hero_Group 
             WHERE GroupID=1
            )

void FilterGroup()
    {
        HDAEntities db = new HDAEntities();
        var query = from obj in db.CharactersNames
                    where obj.ID == from obj2 in db.Hero_Group
                                    where obj2.GroupID == comboBox1.SelectedIndex
                                    select new
                                    {
                                        obj2.GroupID
                                    }
                    select new
                    {
                        obj.ID,
                        obj.HeroName,
                        obj.HeroRarity,
                        obj.Initiative,
                        obj.Attack,
                        obj.Attack1
                    };
    }

void FilterGroup()
{
    HDAEntities db = new HDAEntities();

    var subQuery = db.Hero_Group.Where(h => h.GroupID == comboBox1.selectedIndex)
                                .Select(h => h.GroupID);

    var query = from obj in db.CharactersNames
                where subQuery.Contains(obj.ID)
                select new
                {
                    obj.ID,
                    obj.HeroName,
                    obj.HeroRarity,
                    obj.Initiative,
                    obj.Attack,
                    obj.Attack1
                };

    var result = query.ToList(); // this is where your query and subquery are evaluated and sent to the database

    db.Dispose();
    db = null;
}

但这当然是胡言乱语

---

有人能帮我吗？（请注意，我对LINQ to SQL知之甚少）

---

~TIA~

你可以这样做：

SELECT ID,HeroName,HeroRarity,Initiative,Attack,Attack1 
FROM   CharactersName
WHERE  ID IN(
             SELECT HeroID 
             FROM   Hero_Group 
             WHERE GroupID=1
            )

void FilterGroup()
    {
        HDAEntities db = new HDAEntities();
        var query = from obj in db.CharactersNames
                    where obj.ID == from obj2 in db.Hero_Group
                                    where obj2.GroupID == comboBox1.SelectedIndex
                                    select new
                                    {
                                        obj2.GroupID
                                    }
                    select new
                    {
                        obj.ID,
                        obj.HeroName,
                        obj.HeroRarity,
                        obj.Initiative,
                        obj.Attack,
                        obj.Attack1
                    };
    }

void FilterGroup()
{
    HDAEntities db = new HDAEntities();

    var subQuery = db.Hero_Group.Where(h => h.GroupID == comboBox1.selectedIndex)
                                .Select(h => h.GroupID);

    var query = from obj in db.CharactersNames
                where subQuery.Contains(obj.ID)
                select new
                {
                    obj.ID,
                    obj.HeroName,
                    obj.HeroRarity,
                    obj.Initiative,
                    obj.Attack,
                    obj.Attack1
                };

    var result = query.ToList(); // this is where your query and subquery are evaluated and sent to the database

    db.Dispose();
    db = null;
}

---

请注意，在调用ToList（）之前，不会计算子查询。您还需要处理该对象（或尝试使用语句创建hdaenties对象）。另外，请确保在评估查询之前不处理数据库（在dispose之后调用ToList将引发异常）。

您会遇到什么错误？尝试像这样还原内部查询

where（来自obj2…）.Contains（obj.ID）

where subQuery.Contains（obj.ID）这一行有错误==>where subQuery.Contains（obj.ID）错误3无法将lambda表达式转换为类型“string”，因为它不是委托类型C:\Users\DELL\Documents\Visual Studio 2010\Projects\HDA\u InfoBook\HDA\u InfoBook\ViewAll。cs 104 25 HDA\u InfoBook您的obj.ID和h.GroupID是同一类型的吗？或者obj.ID可能是string？Table（Hero_Group）：herod（smallint），GroupID（tinyint）-Table（CharactersName）：ID（smallint）-Table（Groups）：ID（tinyint）@Cosmin您可以

使用
语句来处理dbcontextWelcome to stackoverflow。请详细说明您的答案并使用代码格式。