Windows apps
Collapse the table of content
Expand the table of content
Information
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.

SortedList<TKey, TValue>::ContainsKey Method (TKey)

 

Determines whether the SortedList<TKey, TValue> contains a specific key.

Namespace:   System.Collections.Generic
Assembly:  System (in System.dll)

public:
virtual bool ContainsKey(
	TKey key
) sealed

Parameters

key
Type: TKey

The key to locate in the SortedList<TKey, TValue>.

Return Value

Type: System::Boolean

true if the SortedList<TKey, TValue> contains an element with the specified key; otherwise, false.

Exception Condition
ArgumentNullException

key is null.

This method is an O(log n) operation, where n is Count.

The following code example shows how to use the ContainsKey method to test whether a key exists prior to calling the Add method. It also shows how to use the TryGetValue method to retrieve values, which is an efficient way to retrieve values when a program frequently tries keys that are not in the sorted list. Finally, it shows the least efficient way to test whether keys exist, by using the Item property (the indexer in C#).

This code example is part of a larger example provided for the SortedList<TKey, TValue> class.

// ContainsKey can be used to test keys before inserting
// them.
if (!openWith->ContainsKey("ht"))
{
    openWith->Add("ht", "hypertrm.exe");
    Console::WriteLine("Value added for key = \"ht\": {0}",
        openWith["ht"]);
}
// When a program often has to try keys that turn out not to
// be in the list, TryGetValue can be a more efficient
// way to retrieve values.
String^ value = "";
if (openWith->TryGetValue("tif", value))
{
    Console::WriteLine("For key = \"tif\", value = {0}.", value);
}
else
{
    Console::WriteLine("Key = \"tif\" is not found.");
}
// The indexer throws an exception if the requested key is
// not in the list.
try
{
    Console::WriteLine("For key = \"tif\", value = {0}.",
        openWith["tif"]);
}
catch (KeyNotFoundException^)
{
    Console::WriteLine("Key = \"tif\" is not found.");
}

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0
Return to top
Show:
© 2017 Microsoft