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

定義

取得與指定索引鍵關聯的值。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 *  -> bool
override this.TryGetValue : 'Key *  -> bool
Public Function TryGetValue (key As TKey, ByRef value As TValue) As Boolean

參數

key
TKey TKey TKey TKey

要取得其值的索引鍵。The key whose value to get.

value
TValue TValue TValue TValue

這個方法傳回時,如果找到索引鍵,則為與指定索引鍵關聯的值,否則為 value 參數的型別預設值。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. 這個參數會以未初始化的狀態傳遞。This parameter is passed uninitialized.

傳回

如果 true 包含具有指定索引鍵的項目,則為 SortedList<TKey,TValue>,否則為 falsetrue if the SortedList<TKey,TValue> contains an element with the specified key; otherwise, false.

實作

例外狀況

範例

此範例示範如何使用TryGetValue方法, 以更有效率的方式來抓取程式中經常嘗試不在已排序清單中之索引鍵的值。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. 相反地, 此範例也會示範Item[TKey]屬性 (中C#的索引子) 在嘗試取出不存在的索引鍵時, 如何擲回例外狀況。For contrast, the example also shows how the Item[TKey] property (the indexer in C#) throws exceptions when attempting to retrieve nonexistent keys.

這個程式碼範例是針對SortedList<TKey,TValue>類別提供之較大範例的一部分。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
// 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

備註

這個方法結合了ContainsKey方法Item[TKey]和屬性的功能。This method combines the functionality of the ContainsKey method and the Item[TKey] property.

如果找不value到索引鍵, 則參數會取得適當的實數值型別TValue預設值; 例如, 整數類型為零 (0)、 false針對布林類型, 以及null參考型別。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.

這個方法會執行二進位搜尋;因此, 這個方法是 O (log n) 運算, 其中nCountThis method performs a binary search; therefore, this method is an O(log n) operation, where n is Count.

適用於

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