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SortedDictionary<TKey,TValue>.TryGetValue(TKey, TValue) Method

  • Reference

Definition

Namespace:
System.Collections.Generic
Assembly:
System.Collections.dll
Assembly:
System.dll
Assembly:
netstandard.dll
Source:
SortedDictionary.cs
Source:
SortedDictionary.cs
Source:
SortedDictionary.cs

Gets the value associated with the specified key.

public:
 virtual bool TryGetValue(TKey key, [Runtime::InteropServices::Out] TValue % value);
public bool TryGetValue (TKey key, out TValue value);
abstract member TryGetValue : 'Key * 'Value -> bool
override this.TryGetValue : 'Key * 'Value -> bool
Public Function TryGetValue (key As TKey, ByRef value As TValue) As Boolean

Parameters

key
TKey

The key of the value to get.

value
TValue

When this method returns, the value associated with the specified key, if the key is found; otherwise, the default value for the type of the value parameter.

Returns

Boolean

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

Implements

TryGetValue(TKey, TValue) TryGetValue(TKey, TValue)

Exceptions

ArgumentNullException

key is null.

Examples

The example shows how to use the TryGetValue method as a more efficient way to retrieve values in a program that frequently tries keys that are not in the dictionary. For contrast, the example also shows how the Item[] property (the indexer in C#) throws exceptions when attempting to retrieve nonexistent keys.

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

// When a program often has to try keys that turn out not to
// be in the dictionary, 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.");
}

' When a program often has to try keys that turn out not to
' be in the dictionary, TryGetValue can be a more efficient 
' way to retrieve values.
Dim value As String = ""
If openWith.TryGetValue("tif", value) Then
    Console.WriteLine("For key = ""tif"", value = {0}.", value)
Else
    Console.WriteLine("Key = ""tif"" is not found.")
End If

// The indexer throws an exception if the requested key is
// not in the dictionary.
try
{
    Console.WriteLine("For key = \"tif\", value = {0}.",
        openWith["tif"]);
}
catch (KeyNotFoundException)
{
    Console.WriteLine("Key = \"tif\" is not found.");
}

' The default Item property throws an exception if the requested
' key is not in the dictionary.
Try
    Console.WriteLine("For key = ""tif"", value = {0}.", _
        openWith("tif"))
Catch 
    Console.WriteLine("Key = ""tif"" is not found.")
End Try

Remarks

This method combines the functionality of the ContainsKey method and the Item[] property.

If the key is not found, then the value parameter gets the appropriate default value for the value type TValue; for example, 0 (zero) for integer types, false for Boolean types, and null for reference types.

This method is an O(log n) operation.

Applies to

See also