IDictionary<TKey, TValue>.TryGetValue Method

Gets the value associated with the specified key.

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

bool TryGetValue(
	TKey key,
	out TValue value
)

Parameters

key
Type: TKey
The key whose value to get.
value
Type: 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.

Return Value

Type: System.Boolean
true if the object that implements IDictionary<TKey, TValue> contains an element with the specified key; otherwise, false.

ExceptionCondition
ArgumentNullException

key is null.

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

The example shows how to use the TryGetValue method to retrieve values. If a program frequently tries key values that are not in a dictionary, the TryGetValue method can be more efficient than using the Item property (the indexer in C#), which throws exceptions when attempting to retrieve nonexistent keys.

This code is part of a larger example that can be compiled and executed. See System.Collections.Generic.IDictionary<TKey, TValue>.


// 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.");
}


...


// 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.");
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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