Question

我正在尝试构造一个linq方法，我可以使用join和where子句验证两个参数，但是目前我收到了一个编译错误 - 在声明它之前不能使用局部变量'query' - error。

 public bool Validate(string username, string password)
    {
        var query = from t in db.Trial_Try
                    join u in db.UserDetails on t.tUID equals u.uID
                    where t.tExpiryDate >= DateTime.Now &&
                    t.tPublication.Value == 163 &&
                    u.uUsername == username &&
                    u.uPassword == password
                   select query.FirstOrDefault();

    }

感谢您的时间和帮助。

Answer 1

应该是

var query = (from t in db.Trial_Try
                join u in db.UserDetails on t.tUID equals u.uID
                where t.tExpiryDate >= DateTime.Now &&
                t.tPublication.Value == 163 &&
                u.uUsername == username &&
                u.uPassword == password
               select t) .FirstOrDefault();

或者如果你不想那些价值观

基本上你试图在你的select子句中使用查询，这不是它所期望的。

Answer 2

var query = from t in db.Trial_Try
                    join u in db.UserDetails on t.tUID equals u.uID
                    where t.tExpiryDate >= DateTime.Now &&
                    t.tPublication.Value == 163 &&
                    u.uUsername == username &&
                    u.uPassword == password
                   select t.FirstOrDefault();

Answer 3

public bool Validate(string username, string password)
    {

        var query = from t in db.Trial_Try
                    join u in db.UserDetails on t.tUID equals u.uID
                    where t.tExpiryDate >= DateTime.Now &&
                    t.tPublication.Value == 163 &&
                    u.uUsername == username &&
                    u.uPassword == password
                    select u; 

        // "execute" the query
        return query.FirstOrDefault() != null; 

    }

如何验证Linq连接查询？

3 个答案: