If Exists Statement in SQL to Linq

if exists statement in sql to linq

It can't be done in LINQ2SQL with a single statement as the LINQ syntax and extension methods don't support inserts. The following (assuming a datacontext named db) should do the trick.

 if (!db.Users.Any( u => u.UserName == "michael" ))
 {
      db.Users.InsertOnSubmit( new User { UserName = "michael" } );
      db.SubmitChanges();
 }

Update value if exist or insert in SQL with C# linq

I found the answer.
Here is the code that uses linq and lambda expressions

        List<KodikosProtimisis> newListKodikosProtimisis = new List<KodikosProtimisis>();
                    newListKodikosProtimisis.Add(new KodikosProtimisis { Kodikos = "100", Perigrafi = "Δασμός τρίτων χωρών έναντι όλων (erga omnes)", TaricTiposMetrou = "103" });
                    newListKodikosProtimisis.Add(new KodikosProtimisis { Kodikos = "110", Perigrafi = "Αυτόνομη δασμολογική αναστολή έναντι όλων (erga omnes) (προσωρινή αναστολή των αυτόνομων δασμών για ορισμένα εμπορεύματα του αγροτικού, χημικού, αεροναυπηγικού και του ηλεκτρονικού τομέα)", TaricTiposMetrou = "112" });
                    newListKodikosProtimisis.Add(new KodikosProtimisis { Kodikos = "420", Perigrafi = "Ποσόστωση τελωνειακής ένωσης", TaricTiposMetrou = "112" });
                    newListKodikosProtimisis.Add(new KodikosProtimisis { Kodikos = "422", Perigrafi = "Ποσόστωση τελωνειακής ένωσης", TaricTiposMetrou = "112" });
    .
    .
    .
    more values
                    foreach (var kodikosProtimisis in newListKodikosProtimisis)
                    {

                        using (Ektel db = new Ektel(EktelDataContextManager.ConnectionString))
                        {

                            var qry = db.KodikosProtimisis.Where(x => x.Kodikos == kodikosProtimisis.Kodikos).FirstOrDefault();

                            if (qry != null)
                            {
                                // The value exists .Update
                                qry.Kodikos = kodikosProtimisis.Kodikos;
                                qry.Perigrafi = kodikosProtimisis.Perigrafi;
                                qry.TaricTiposMetrou = kodikosProtimisis.TaricTiposMetrou;
                            }
                            else
                            {
                                //The value doesnt exist.Insert.
                                db.KodikosProtimisis.InsertOnSubmit(new KodikosProtimisis
                                {
                                    Kodikos = kodikosProtimisis.Kodikos,
                                    Perigrafi = kodikosProtimisis.Perigrafi,
                                    TaricTiposMetrou = kodikosProtimisis.TaricTiposMetrou
                                });
                            }

                        db.SubmitChanges();
                    }

                }

How to do a SQL Where Exists in LINQ to Entities?

The .Any() extension method typically maps to exists.

SQL Query to LINQ syntax using not exist and join

You can try like this:

(from lk in localizationKey    
where (from l in lang
        join lv in localizationValue on l.Id equals lv.LanguageId
        where (l.Title == "en-US" && lv.LocalizationKeyId == lk.Id)   
       select l).FirstOrDefault() == null
 select lk).ToList();

or

(from lk in localizationKey    
where !(from l in lang
        join lv in localizationValue on l.Id equals lv.LanguageId
        where !(l.Title == "en-US" && lv.LocalizationKeyId == lk.Id) 
        select l).FirstOrDefault().Any()
 select lk).ToList();

LINQ Query problem. Need to check if exists

Based on the updated question, and if I understand it correctly, I think this solution will work for you.

var urlNameExists = _sb.Any(x => x.UrlName == urlName && x.Id != currentEditId);

if (urlNameExists)
     throw Exception("A record with that UrlName already exists");

TryUpdateModel(existingMenu);
_menu.Add();

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