I want to convert from IEnumerable<Contact>
to List<Contact>
. How can I do this?
You can do this very simply using LINQ.
Make sure this using is at the top of your C# file:
using System.Linq;
Then use the ToList
extension method.
Example:
IEnumerable<int> enumerable = Enumerable.Range(1, 300);
List<int> asList = enumerable.ToList();
In case you're working with a regular old System.Collections.IEnumerable
instead of IEnumerable<T>
you can use enumerable.Cast<object>().ToList()
If you're using an implementation of System.Collections.IEnumerable
you can do like following to convert it to a List
. The following uses Enumerable.Cast method to convert IEnumerable
to a generic List
.
// ArrayList implements IEnumerable interface
ArrayList _provinces = new System.Collections.ArrayList();
_provinces.Add("Western");
_provinces.Add("Eastern");
List<string> provinces = _provinces.Cast<string>().ToList();
If you're using Generic version IEnumerable<T>
, The conversion is straight forward. Since both are generics, you can do like below,
IEnumerable<int> values = Enumerable.Range(1, 10);
List<int> valueList = values.ToList();
But if the IEnumerable
is null, when you try to convert it to a List
, you'll get an ArgumentNullException
saying Value cannot be null.
IEnumerable<int> values2 = null;
List<int> valueList2 = values2.ToList();
Therefore as mentioned in the other answer, remember to do a null
check before converting it to a List
.
I use an extension method for this. My extension method first checks to see if the enumeration is null and if so creates an empty list. This allows you to do a foreach on it without explicitly having to check for null.
Here is a very contrived example:
IEnumerable<string> stringEnumerable = null;
StringBuilder csv = new StringBuilder();
stringEnumerable.ToNonNullList().ForEach(str=> csv.Append(str).Append(","));
Here is the extension method:
public static List<T> ToNonNullList<T>(this IEnumerable<T> obj)
{
return obj == null ? new List<T>() : obj.ToList();
}
another way
List<int> list=new List<int>();
IEnumerable<int> enumerable =Enumerable.Range(1, 300);
foreach (var item in enumerable )
{
list.Add(item);
}
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