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c#linqentity-framework
Raman
Raman

Reputation: 35

Entity framework with Linq

I have following method. I need to return var tynames by method so what would be the return type of the method will it be List<string> or something else and also what is the use of FirstOrDefault().

Thanks in advance for your reply

public static List<string> AppType()
{
    var context = new Dll_IssueTracking.IssuTrackingEntities();// Object context defined in Dll_IssuTracking DLL

    var query = from c in context.ApplicationTypes//Query to find TypeNames
                select new { c.TypeName };
    var **TypeNames** = query.FirstOrDefault();
}

Upvotes: 0

Views: 115

Answers (3)

alf
alf

Reputation: 18530

FirstOrDefault returns the first element found, or the default value (which is null in this case) if the query returned no results. In this case the return value of the method should be ApplicationType:

public static ApplicationType AppType()   
{
    var context = new Dll_IssueTracking.IssuTrackingEntities(); // Object context defined in Dll_IssuTracking DLL

    var query = from c in context.ApplicationTypes //Query to find TypeNames
                    select new { c.TypeName };
    return query.FirstOrDefault();
}

Upvotes: 1

Roland Mai
Roland Mai

Reputation: 31077

FirstOrDefault is an extension method which looks something like this:

public T FirstOrDefault>T>(this IEnumerable<T> query)
{
    return query.Any() ? query.First() : default(T);
}

So, it returns the first element in the sequence if it is not empty, or the default of the type if the sequence is empty.

For Instance, if you have an Enumerable<LinqEntity>, then most likely default(LinqEntity) is null. If you had something like Enumerable<int> then default(int) is 0.

Upvotes: 0

Aghilas Yakoub
Aghilas Yakoub

Reputation: 28970

FirstOrDefault return first element in sequence, in this sample ApplicationTypes is your sequence or a default value if the sequence contains no elements.

Upvotes: 0

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