Entity framework with Linq

Question

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();
}

The documentation for FirstOrDefault<T>() can be found here: msdn.microsoft.com/en-us/library/bb340482.aspx. It returns an object of type T. — Robert Harvey
– Robert Harvey, Commented Aug 26, 2012 at 16:26

alf · Accepted Answer · 2012-08-26 16:42:07Z

1

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();
}

edited Aug 26, 2012 at 16:42

answered Aug 26, 2012 at 16:30

alf

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4 Comments

Robert Harvey Over a year ago

Actually, it returns default(T) if there are no results. It will return null in this particular case.

Raman Over a year ago

thanks..I have 3 typenames ( CUSTOM,STANDARD,NORMAL) can you please advise the code how to use this method and store values in a dropdownlist

alf Over a year ago

@Raman that depends on what kind of application you're developing and what framework youre using. Please open a separate question and show what you have so far.

Robert Harvey Over a year ago

@Raman: But be cautious... Attempting to build an application piece by piece by asking questions on Stack Overflow isn't going to work. Pick your battles; work for awhile until you get stuck, and then ask a question here. Read MSDN or a book if you need detailed background information to complete your app.

Aghilas Yakoub · Accepted Answer · 2012-08-26 16:29:30Z

0

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

answered Aug 26, 2012 at 16:29

Aghilas Yakoub

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1 Comment

Raman Over a year ago

Thanks Candie...one more thing how can i return var value like in above example I want to return Typenames

Roland Mai · Accepted Answer · 2012-08-26 16:35:55Z

0

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.

answered Aug 26, 2012 at 16:35

Roland Mai

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