CODEWITHSUNDEEP
linqc#-4.0
user1202606
user1202606

Reputation: 1160

linq how to get values from var

How do I get the individual values from the following LINQ query? (I want to get the value for DecalExpireDate, DecalExpireMonth, and DecalExpireYear.)

var previousExpirationDate = (from d in db.CT_Decals
                              where d.TankID == decal.TankID
                              && d.DecalStatus == "Approved"
                              select new
                              {
                                  d.DecalExpireDate,
                                  d.DecalExpireMonth,
                                  d.DecalExpireYear
                              }).Max(d => d.DecalExpireDate);

Upvotes: 4

Views: 21525

Answers (4)

Mong Zhu
Mong Zhu

Reputation: 23732

Building up on Tim and Dipin, the First() method throws unfortunately an InvalidOperationException when the query does not yield any results.

Either you surround it with a try/catch block

try{
    var latest = (from d in db.CT_Decals
                 where d.TankID == decal.TankID && d.DecalStatus == "Approved"
                 orderby d.DecalExpireDate descending
                 select new
                 {
                     d.DecalExpireDate,
                     d.DecalExpireMonth,
                     d.DecalExpireYear
                  }).First();
    var decalExpireDate  = latest.DecalExpireDate;
    var decalExpireMonth = latest.DecalExpireMonth;
    var decalExpireYear  = latest.DecalExpireYear;
}
catch(InvalidOperationException ex){ // tell no Result!}

or you could use FirstOrDefault() which will return a null-reference when the query yields no match.

//... Example from above

}).FirstOrDefault();

// check for null-reference
if(latest != null)
    var decalExpireDate  = latest.DecalExpireDate;
    var decalExpireMonth = latest.DecalExpireMonth;
    var decalExpireYear  = latest.DecalExpireYear;
}

A third possibility could be to take the first Element using Take(1)

//... Example from above

}).Take(1).ToList();  // returns an empty list if no match

// check whether something was returned
if(latest.Any())
    var decalExpireDate  = latest[0].DecalExpireDate;
    var decalExpireMonth = latest[0].DecalExpireMonth;
    var decalExpireYear  = latest[0].DecalExpireYear;
}

Upvotes: 0

user2674838
user2674838

Reputation: 1

var q = from r in tab1.dictenaries
                    select new {
                        r.ENGLISH,
                        r.FRENCH
                    };

            List<SomeClass> sml = new List<SomeClass>();

            int starting = 10;
            int ending = 20;
            int cntr = 0;
           foreach( var verObj in q)
           {
               if (cntr >= starting && cntr <= ending)
               {
                   SomeClass sm1 = new SomeClass();
                   sm1.ENGLISH = verObj.ENGLISH.ToString();
                   sm1.FRENCH = verObj.FRENCH.ToString();
                   sml.Add(sm1);
               }
               else if(cntr >ending)
               {
                   break;
               }
               cntr = cntr + 1;
           }

Upvotes: 0

Dipin Behl
Dipin Behl

Reputation: 123

Making the same assumptions as Tim, you could also go with

var result = db.CT_Decals.OrderByDescending(d => d.DecalExpireDate).First(d => d.TankID == decal.TankID && d.DecalStatus == "Approved");

var expireDate = result.DecalExpireDate;
var expireMonth = result.DecalExpireMonth; 
var expireYear = result.DecalExpireYear;

You will have the desired object of type 'CT_Decals' in 'result' variable so access any property of it

Upvotes: 0

Tim Schmelter
Tim Schmelter

Reputation: 460118

I assume you want to get the DecalExpireDate, DecalExpireMonth, and DecalExpireYear from the element with the highest (last) DecalExpireDate. Then you could order by this date:

var latest = (from d in db.CT_Decals
             where d.TankID == decal.TankID && d.DecalStatus == "Approved"
             orderby d.DecalExpireDate descending
             select new
             {
                 d.DecalExpireDate,
                 d.DecalExpireMonth,
                 d.DecalExpireYear
              }).First();
var decalExpireDate  = latest.DecalExpireDate;
var decalExpireMonth = latest.DecalExpireMonth;
var decalExpireYear  = latest.DecalExpireYear;

Upvotes: 11

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