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How do I empty my IEnumerable?

by Rhyley Bryan

How do I empty my IEnumerable?

The Empty() method caches an empty sequence of type TResult. When the object it returns is enumerated, it yields no elements. An enumerable sequence with no elements is different from null . If you return null for IEnumerable<T> and then attempt to enumerate it, you will receive a NullReferenceException .

How do I check if my IEnumerable is empty?

  1. Count == 0 is just fine….
  2. Count() only iterates the enumeration if it can’t be cast to an ICollection.
  3. If you are working with an IEnumerable, using Count() to test for emptyness is definitely a bad idea since the Linq implementation WILL iterate over the entire collection, while Any will just move the iterator once.

How do I know if IEnumerable has value?

“check if ienumerable is empty c#” Code Answer

  1. IEnumerable enumerable = new List();
  2. ​
  3. if(! enumerable. Any())
  4. {
  5. throw new InvalidOperationException();
  6. }

Does any () check for NULL?

As others have already mentioned, Any checks whether or not a sequence contains elements. It does not prevent you from passing null values(what might the bug in the first place). Every extension method in Enumerable class throws an an ArgumentNullException if the source is null .

Can IEnumerable return null?

5 Answers. You do not need to check if selectedRows is null . The returned IEnumerable<> might be empty, but it will never be null .

Is it better to return null or empty list?

It is better to return empty collections rather than null when writing methods. The reason being that any code calling your method then doesn’t need to explicitly handle a special null case. Returning an empty collection makes the null check redundant and results in much cleaner method calling code.

Can IEnumerable be null?

Is Empty List C#?

Check if a list is empty in C#

  • Using Enumerable. Any() method ( System. Linq )
  • Using Enumerable.FirstOrDefault() method ( System.Linq ) The Enumerable.FirstOrDefault() method returns the first element of a sequence.
  • Using Enumerable. Count() method ( System.

How is IEnumerable count calculated?

In its simplest form (without any parameters), the Count() method returns an int indicating the number of elements in the source sequence. IEnumerable strings = new List { “first”, “then”, “and then”, “finally” }; // Will return 4 int result = strings. Count();

Is null false in C?

13 Answers. Yes. NULL evaluates to false, since C considers any non-zero value true and any zero value false.

Is string null or empty C#?

In C#, IsNullOrEmpty() is a string method. It is used to check whether the specified string is null or an Empty string. A string will be null if it has not been assigned a value.

Should I use null or empty string?

Key things to take away are that there is no difference in table size, however some users prefer to use an empty string as it can make queries easier as there is not a NULL check to do. You just check if the string is empty. Another thing to note is what NULL means in the context of a relational database.

When to use empty in IEnumerable < T >?

The elements of each array in the collection are added to the resulting IEnumerable only if that array contains four or more elements. Empty is used to generate the seed value for Aggregate because if no array in the collection has four or more elements, only the empty sequence is returned. ‘ Create three string arrays.

How to use the dim method in IEnumerable?

Dim empty As IEnumerable(Of Decimal) = Enumerable.Empty(Of Decimal)() The following code example demonstrates a possible application of the Empty () method. The Aggregate method is applied to a collection of string arrays.

How to create an empty sequence in LINQ?

Linq Returns an empty IEnumerable that has the specified type argument. The type to assign to the type parameter of the returned generic IEnumerable . An empty IEnumerable whose type argument is TResult. The following code example demonstrates how to use Empty () to generate an empty IEnumerable . ‘ Create an empty sequence.

When to use take and skip in LINQ?

If count is less than or equal to zero, source is not enumerated and an empty IEnumerable is returned. The Take and Skip methods are functional complements. Given a sequence coll and an integer n, concatenating the results of coll.Take (n) and coll.Skip (n) yields the same sequence as coll.