Error in LINQ query execution

Question

I'm trying to get values from database it is working perfect with raw sql query but not working with linq. I'm sharing my code please guide me

LINQ:

using (var db = new SContext())
{
    var abc = db.Locales
                .Where(c => c.Culture == cultureName && c.Key == key)
                .Select(a => a.Value);

   return abc.ToString();
}

SQL RAW (Working Perfect)

using (var conn = new SqlConnection(_connectionString))
{
    using (var cmd = conn.CreateCommand())
    {
        cmd.CommandText = "SELECT [Value] FROM [Spenotics].[dbo].[Locale] WHERE [Key] = @key AND [Culture] = @culture";
        cmd.Parameters.AddWithValue("key", key);
        cmd.Parameters.AddWithValue("culture", cultureName);
        conn.Open();
        var value = cmd.ExecuteScalar();
        return (string)value;
     }
}

I want to convert sql query in to linq but it is giving error "object reference not set to an instance of an object"

Please use http://stackoverflow.com/q/4660142/87698 to determine *where exactly* the exception occurs. — Heinzi, Jul 09 '14 at 22:37
Add a `.First()` to the end of your linq statement, after the select? That should give you the value instead of an IQueryable of values. — Sarah Bailey, Jul 09 '14 at 22:37
@SarahBourt I have used your method but it is giving this error "Sequence contains no elements" — DevWithSigns, Jul 09 '14 at 22:39

score 0 · Accepted Answer · answered Jul 09 '14 at 23:45

Whenever you needs only one element from the query then it would be ideal to use one of the bellow

. First() - throws if empty/not found, does not throw if duplicate

. FirstOrDefault() - returns default if empty/not found, does not throw if duplicate

. Single() - throws if empty/not found, throws if duplicate exists

. SingleOrDefault() - returns default if empty/not found, throws if duplicate exists

var abc = db.Locales
                .Where(c => c.Culture == cultureName && c.Key == key)
                .Select(a => a.Value).FirstOrDefault();

In SQL raw also it would be ideal to use TOP 1

SELECT TOP 1 [Value] FROM [Spenotics].[dbo].[Locale] WHERE [Key] = @key AND [Culture] = @culture

Error in LINQ query execution

1 Answers1