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Posted 22 Dec 2012
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Cast an IEnumerable to an IEnumerable(T)

, 22 Dec 2012
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In this tip, I tell you how to cast an IEnumerable to an IEnumerable(T)

Introduction

It's possible to use LINQ queries to get data from an IEnumerable<T>. But for an IEnumerable, you can't use LINQ. If you write this LINQ query for an IEnumerable:

IEnumerable ienumerable = new int[] { 1, 5, 6, 7, 8, 11, 10, 134, 90 };
var integer = from i in ienumerable where i > 10 select i;

Then, you get this error:

Could not find an implementation of the query pattern for 
source type 'System.Collections.IEnumerable'. 'Where' not found. 
Consider explicitly specifying the type of the range variable 'i'. 

In this tip, I tell you how to cast an IEnumerable to an IEnumerable<T>.

Cast an IEnumerable to an IEnumerable<T>

To cast an IEnumerable to an IEnumerable<T>, you can use this code:

IEnumerable ienumerable = new int[] { 1, 5, 6, 7, 8, 11, 10, 134, 90 };
IEnumerable casted = ienumerable.Cast<int>(); // change 'int' into the 
                              //type of the elements in your IEnumerable

Now, you can use a LINQ query for casted. But, an IEnumerable can contain different types:

IEnumerable ienumerable = new object[] { 1, 5, 6, 7, 8, 11, 10, 134, 90, "test" };

With this code, you can get all integers from the IEnumerable into a IEnumerable<T> using the OfType<T> function:

IEnumerable ienumerable = new object[] { 1, 5, 6, 7, 8, 11, 10, 134, 90, "test" };
IEnumerable<int> allIntegers = ienumerable.OfType<int>(); // change 'int' 
      // in the type of the elements you want to get from the IEnumerable

Points of Interest

There're many collection classes in C# that inherit from IEnumerable, for example System.Windows.Forms.Control.ControlCollection, System.Windows.Forms.HtmlElementCollection or System.Xml.XmlNodeList class. It's useful to use LINQ for these classes.

History

  • 22 Dec 2012: First version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Thomas Daniels
Student
Belgium Belgium
Also known as ProgramFOX. I like programming, playing chess and astronomy. Administrator of Chess Variants Training[^].

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Comments and Discussions

 
GeneralMy vote of 5 Pin
Tarek Elqusi23-Dec-12 6:27
professionalTarek Elqusi23-Dec-12 6:27 
GeneralRe: My vote of 5 Pin
Thomas Daniels23-Dec-12 23:51
mveThomas Daniels23-Dec-12 23:51 
Questiongood Pin
UllasN22-Dec-12 21:23
memberUllasN22-Dec-12 21:23 
AnswerRe: good Pin
Thomas Daniels22-Dec-12 22:46
mveThomas Daniels22-Dec-12 22:46 
GeneralRe: good Pin
UllasN23-Dec-12 0:12
memberUllasN23-Dec-12 0:12 

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