List(T).AsReadOnly Method

Returns a read-only IList(T) wrapper for the current collection.

Namespace:  System.Collections.Generic
Assemblies:   mscorlib (in mscorlib.dll)
  System.Collections (in System.Collections.dll)

member AsReadOnly : unit -> ReadOnlyCollection<'T> 

Return Value

Type: System.Collections.ObjectModel.ReadOnlyCollection(T)
A ReadOnlyCollection(T) that acts as a read-only wrapper around the current List(T).

To prevent any modifications to List(T), expose List(T) only through this wrapper. A ReadOnlyCollection(T) does not expose methods that modify the collection. However, if changes are made to the underlying List(T), the read-only collection reflects those changes.

This method is an O(1) operation.

The following example demonstrates the AsReadOnly method. A List(T) of strings with a capacity of 4 is created, because the ultimate size of the list is known to be exactly 4. The list is populated with four strings, and the AsReadOnly method is used to get a read-only IList(T) generic interface implementation that wraps the original list.

An element of the original list is set to "Coelophysis" using the Item property (the indexer in C#), and the contents of the read-only list are displayed again to demonstrate that it is just a wrapper for the original list.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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