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

 
System_CAPS_noteNote

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

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

public bool ContainsKey(
	TKey key
)

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", out 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
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