The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

ReadOnlyCollection<T>.IndexOf Method

Searches for the specified object and returns the zero-based index of the first occurrence within the entire ReadOnlyCollection<T>.

Namespace:  System.Collections.ObjectModel
Assembly:  mscorlib (in mscorlib.dll)

public int IndexOf(
	T value


Type: T
The object to locate in the List<T>. The value can be null for reference types.

Return Value

Type: System.Int32
The zero-based index of the first occurrence of item within the entire ReadOnlyCollection<T>, if found; otherwise, -1.



The ReadOnlyCollection<T> is searched forward starting at the first element and ending at the last element.

This method determines equality using the default comparer EqualityComparer<T>.Default.

This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.


Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Was this page helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

© 2015 Microsoft