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

Reference

Definition

Namespace:: System.Collections.Generic

Assemblies:: System.dll, System.Collections.dll

Assembly:: System.Collections.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Source:: SortedList.cs

Source:: SortedList.cs

Source:: SortedList.cs

Important

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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 whose 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. This parameter is passed uninitialized.

Returns

Boolean

true if the SortedList<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 sorted list. 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 SortedList<TKey,TValue> class.

// 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.");
}

// 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.");
}

' 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.
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

// 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.
match openWith.TryGetValue("tif") with
| true, value ->
    printfn "For key = \"tif\", value = {value}."
| false, _ ->
    printfn "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.");
}

// 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.");
}

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

// The indexer throws an exception if the requested key is
// not in the list.
try
    printfn $"""For key = "tif", value = {openWith["tif"]}."""
with 
    | :? KeyNotFoundException ->
        printfn "Key = \"tif\" is not found."

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, zero (0) for integer types, false for Boolean types, and null for reference types.

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

Applies to

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