在IQueryable<T>中搜索

Question

我正在通过下面的行从数据库中提取一些数据：

IQueryable<user> UserList = DatabaseContext.Users.GetAll();

我想在用户列表中查找一些内容，例如：

foreach (var User in UserList)
{
    if (User.type == (int)UserType.SuperUser)
    {
        IsRecordFound = true;
        break;
    }
}

然后我根据标志的状态做一些事情：

if (!IsRecordFound)
{
    AesCrypto aesCrypto = new AesCrypto();
    user newuser = new user();
    newuser.username = DEFAULT_SUPER_USER_NAME;
    newuser.password = aesCrypto.Encrypt(DEFAULT_SUPER_USER_PASSWORD);
    newuser.type = (int)UserType.SuperUser;
    newuser.create_date = DateTime.Now;
    newuser.last_login = newuser.create_date;
    newuser.email_address = DEFAULT_SUPER_USER_EMAIL_ADDR;
    newuser.login_count = 1;
    DatabaseContext.Users.Add(newuser);
    if (!DatabaseContext.Save())
        return false;
}

有没有什么简单实用的方法可以通过使用LINQ或其他东西在IQueryable接口中搜索？

Answer 1

if (!UserList.Any(x => x.Type == (int)UserType.SuperUser))
{
    AesCrypto aesCrypto = new AesCrypto();
    user newuser = new user();
    newuser.username = DEFAULT_SUPER_USER_NAME;
    newuser.password = aesCrypto.Encrypt(DEFAULT_SUPER_USER_PASSWORD);
    newuser.type = (int)UserType.SuperUser;
    newuser.create_date = DateTime.Now;
    newuser.last_login = newuser.create_date;
    newuser.email_address = DEFAULT_SUPER_USER_EMAIL_ADDR;
    newuser.login_count = 1;
    DatabaseContext.Users.Add(newuser);
    if (!DatabaseContext.Save())
        return false;
}

Answer 2

你可以像一样完成

bool isSuperUser =  UserList.Any(a=>a.type==a.SuperUser)

Answer 3

要搜索IQueryable，请使用where

var foundUsers = UserList.Where( usr => usr.Type == (int)UserTypes.SuperUser );
if( foundUsers == null && foundUsers.Count() == 0 ) // only one of these is required.. I forget which though :s
{
    AesCrypto aesCrypto = new AesCrypto();
    user newuser = new user();
    newuser.username = DEFAULT_SUPER_USER_NAME;
    newuser.password = aesCrypto.Encrypt(DEFAULT_SUPER_USER_PASSWORD);
    newuser.type = (int)UserType.SuperUser;
    newuser.create_date = DateTime.Now;
    newuser.last_login = newuser.create_date;
    newuser.email_address = DEFAULT_SUPER_USER_EMAIL_ADDR;
    newuser.login_count = 1;
    DatabaseContext.Users.Add(newuser);
    if (!DatabaseContext.Save())
        return false;
}

Answer 4

UserList .Where(user => user.Type== (int)UserType.SuperUser);