Match and update values using linq from two lists?

Question

Hi I am new to the c# and Linq. I am trying to update the one list if the value of some property matches the value of the other lists property.

Suppose i have one list as firstlist

   Name      code        
   ABC       101         
   DEF       201         
   GHI       301
   JKL       401
   MNO       101 

And Second list as secondlist

  description       Code
    IT               101
    ADMIN            201
    Develeopment     301
    Testing          401
    Service          501

And i want my resultant list as

    Name      code        
    ABC       101 IT        
    DEF       201 ADMIN       
    GHI       301 Develeopment
    JKL       401 Testing
    MNO       101 IT

I tried something like this ,

    var query = firstlist.Select(x => { x.Code = 101; return x.Code.ToString()+"IT"; })

But i want to match the code from the secondlist in place of 101 and for matching code i want to update the firstlist code with the code+description i don't have any idea how to do it if anyone suggest any way or link which will guide me would be great.

*******UPDATE*******

What i want to say is that as @Sergey suggested

   from x in firstlist
   join y in secondList
   on x.code equals y.Code
   select new {
       x.Name,
      code = String.Format("{0} {1}", y.Code, y.description)   
  }

in place of this can i just do something like this

   from x in firstlist
   join y in secondList
   on x.code equals y.Code
   select x.code = String.Format("{0} {1}", y.Code, y.description)   

which will only update the existing listone in place of the creating new entity for each match

Solution

Use Enumerable.Join to get items which match in both lists:

from x in firstlist
join y in secondList
   on x.code equals y.Code
select new {
   x.Name,
   code = String.Format("{0} {1}", y.Code, y.description)   
}

Updating objects in first list:

var query = from x in firstlist
            join y in secondList
                on x.code equals y.Code
            select new { x, y };

foreach(var match in query)
   match.x.Code = String.Format("{0} {1}", match.y.Code, match.y.description);

Comments

[Admin]

what if i have the very long list of properties in the listone do i have to mention all of them in this code = String.Format("{0} {1}", y.Code, y.description),someprop1,someprop2,someprop3 like this

[Sergey Berezovskiy]

@Curiosity if you are talking about firstlist and properties of x then you can simply select x entity in result: select new { x, y }

[Sergey Berezovskiy]

@Curiosity where someprop1, someprop2 comes from?

[Admin]

They are extra properties in the firstlist other than name and code so what i am saying is in place creating new entity for each match can i just update the existing value of the code by doing something like x.code=y.code+y.description

[Sergey Berezovskiy]

@Curiosity if you want to update items from firstlist, then you can enumerated results of query and update x.Code