SortedList<TKey,TValue>.ContainsKey(TKey) 方法

public:
 virtual bool ContainsKey(TKey key);

public bool ContainsKey (TKey key);

abstract member ContainsKey : 'Key -> bool
override this.ContainsKey : 'Key -> bool

Public Function ContainsKey (key As TKey) As Boolean

参数

返回

实现

异常

示例

下面的代码示例演示如何使用ContainsKey方法来测试在Add调用方法之前是否存在某个键。The following code example shows how to use the ContainsKey method to test whether a key exists prior to calling the Add method. 它还演示了如何使用TryGetValue方法检索值，这是在程序频繁尝试排序列表中没有的键时检索值的有效方法。It also shows how to use the TryGetValue method to retrieve values, which is an efficient way to retrieve values when a program frequently tries keys that are not in the sorted list. 最后，它通过使用Item[TKey]属性（中C#的索引器）来显示测试项是否存在的效率最低的方法。Finally, it shows the least efficient way to test whether keys exist, by using the Item[TKey] property (the indexer in C#).

此代码示例是为SortedList<TKey,TValue>类提供的更大示例的一部分。This code example is part of a larger example provided for the SortedList<TKey,TValue> class.

// ContainsKey can be used to test keys before inserting
// them.
if (!openWith->ContainsKey("ht"))
{
    openWith->Add("ht", "hypertrm.exe");
    Console::WriteLine("Value added for key = \"ht\": {0}",
        openWith["ht"]);
}

// ContainsKey can be used to test keys before inserting 
// them.
if (!openWith.ContainsKey("ht"))
{
    openWith.Add("ht", "hypertrm.exe");
    Console.WriteLine("Value added for key = \"ht\": {0}", 
        openWith["ht"]);
}

' ContainsKey can be used to test keys before inserting 
' them.
If Not openWith.ContainsKey("ht") Then
    openWith.Add("ht", "hypertrm.exe")
    Console.WriteLine("Value added for key = ""ht"": {0}", _
        openWith("ht"))
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.
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

注解

此方法的运算复杂度为 O n（log）， n其中Count，为。This method is an O(log n) operation, where n is Count.

适用于

另请参阅

• IndexOfKey(TKey)
• ContainsValue(TValue)