我如何获取linq收到的信息，并在if else语句中使用该信息？

Question

I have this LINQ that works just fine:

var checkIFExist = (from row in db.Following
                      where follow.UserName == checkUserNameInLinq 
                         && follow.FollowThisUser == FollowUsername 
                         && follow.isFollowing == true
                      select row).ToList();

If all values are correct, I would like to use them in an if else statement. for example:

if (checkIFExist == ALL 3 VALUES IN LINQ IS CORRECT)
{
   Index();
}

Answer 1

Your linq query returns rows which meet your conditions:

var rowsMeetingCriteria = from row in db.Following
                          where (... conditions ...)
                          select row;

Now, on which condition do you want to perform an action? If you want to do something if there's at least one row retunred by the query, use .Any() method:

if (rowsMeetingCriteria.Any())
{
    // code
}

If you have any other needs, take a look at methods available for Enumerables here . You can also put your query inside the Any method, like below, but when the query has few parts you should probably do it separately as above (better readability):

if (rowsMeetingCriteria.Any(row => row.Field1 == ... && row.Field2 > ...)
{
    // code
}