How to access the first element in an object which implemented IEnumerable

Only want to access the first element in an object which implemented IEnumerable, how t开发者_Python百科o do that?

Unfortunately you can’t use the LINQ extension methods on something which implements only IEnumerable. You can, however, use .Cast<object>() to turn it into an IEnumerable<object> and then use the following methods. The following assumes that collection is of type IEnumerable<T> for some T:

To access the first element and throw an exception if there is none:

collection.First()

To access the first element and get the type’s default value if there is none:

collection.FirstOrDefault()

The type’s default value is null for reference types (types declared as class, for example string, Stream, Bitmap, etc.) and the “zero value” for value types (types declared as struct or enum, for example int, bool, DateTime, etc.).

To only find out whether there is a first element at all:

collection.Any()

All three of these can take a lambda expression as a condition, e.g. .First(x => x.Name == "x"), which is equivalent to .Where(x => x.Name == "x").First().

use the FirstOrDefault method

using System.Linq;

int[] numbers = { };
int first = numbers.FirstOrDefault();