可以在C＃和LINQ Lambda表达式中使用“ in”类型语句吗？

Question

I need from time to time to compare a number of values like:

if (myCurrentUser.Role in ("Admin","User"))

But it seems the above may not be possible, and instead one needs to do:

if (myCurrentUser.Role == "Admin" || myCurrentUser.Role == "User")

Which starts to gets quite long.

So is there a way to have an "in" approach. Obviously one can do this in SQL.

Also I would like to use this in LINQ Lambda expressions as well.

var myRecords = db.mytable.where(r=>r.name in ("Roy","Jack"))

currently I write this as:

var myRecords = db.mytable.where(r=>((r.name == "Roy")||(r.name == "Jack")));

Thanks in advance.

Answer 1

You can do it with Contains . Try this:

var names = new List<string>() { "Roy", "Jack" };
db.mytable.Where(r => names.Contains(r.name));

Answer 2

尝试使用contains，例如：

var x = (new string[] {"A", "B"}).Contains("C");

Answer 3

If you add this extension method:

public static class Extensions
{
    public static bool IsIn<T>(this T source, params T[] values)
    {
        return values.Contains(source);
    }
}

You can write code like this:

if (myCurrentUser.Role.IsIn("Admin","User"))