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

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

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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