SortedDictionary<TKey,TValue> Class

Definition

Represents a collection of key/value pairs that are sorted on the key.

generic <typename TKey, typename TValue>
public ref class SortedDictionary : System::Collections::Generic::ICollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IDictionary<TKey, TValue>, System::Collections::Generic::IEnumerable<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyCollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyDictionary<TKey, TValue>, System::Collections::IDictionary
[System.Serializable]
public class SortedDictionary<TKey,TValue> : System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IDictionary<TKey,TValue>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyDictionary<TKey,TValue>, System.Collections.IDictionary
type SortedDictionary<'Key, 'Value> = class
    interface IDictionary<'Key, 'Value>
    interface IDictionary
    interface IReadOnlyDictionary<'Key, 'Value>
    interface ICollection<KeyValuePair<'Key, 'Value>>
    interface seq<KeyValuePair<'Key, 'Value>>
    interface IEnumerable
    interface ICollection
    interface IReadOnlyCollection<KeyValuePair<'Key, 'Value>>
Public Class SortedDictionary(Of TKey, TValue)
Implements ICollection(Of KeyValuePair(Of TKey, TValue)), IDictionary, IDictionary(Of TKey, TValue), IEnumerable(Of KeyValuePair(Of TKey, TValue)), IReadOnlyCollection(Of KeyValuePair(Of TKey, TValue)), IReadOnlyDictionary(Of TKey, TValue)

Type Parameters

TKey

The type of the keys in the dictionary.

TValue

The type of the values in the dictionary.

Inheritance
SortedDictionary<TKey,TValue>
Attributes
Implements

Examples

The following code example creates an empty SortedDictionary<TKey,TValue> of strings with string keys and uses the Add method to add some elements. The example demonstrates that the Add method throws an ArgumentException when attempting to add a duplicate key.

The example uses the Item[TKey] property (the indexer in C#) to retrieve values, demonstrating that a KeyNotFoundException is thrown when a requested key is not present, and showing that the value associated with a key can be replaced.

The example shows how to use the TryGetValue method as a more efficient way to retrieve values if a program often must try key values that are not in the dictionary, and it shows how to use the ContainsKey method to test whether a key exists before calling the Add method.

The example shows how to enumerate the keys and values in the dictionary and how to enumerate the keys and values alone using the Keys property and the Values property.

Finally, the example demonstrates the Remove method.

using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        // Create a new sorted dictionary of strings, with string
        // keys.
        SortedDictionary<string, string> openWith = 
            new SortedDictionary<string, string>();

        // Add some elements to the dictionary. There are no 
        // duplicate keys, but some of the values are duplicates.
        openWith.Add("txt", "notepad.exe");
        openWith.Add("bmp", "paint.exe");
        openWith.Add("dib", "paint.exe");
        openWith.Add("rtf", "wordpad.exe");

        // The Add method throws an exception if the new key is 
        // already in the dictionary.
        try
        {
            openWith.Add("txt", "winword.exe");
        }
        catch (ArgumentException)
        {
            Console.WriteLine("An element with Key = \"txt\" already exists.");
        }

        // The Item property is another name for the indexer, so you 
        // can omit its name when accessing elements. 
        Console.WriteLine("For key = \"rtf\", value = {0}.", 
            openWith["rtf"]);

        // The indexer can be used to change the value associated
        // with a key.
        openWith["rtf"] = "winword.exe";
        Console.WriteLine("For key = \"rtf\", value = {0}.", 
            openWith["rtf"]);

        // If a key does not exist, setting the indexer for that key
        // adds a new key/value pair.
        openWith["doc"] = "winword.exe";

        // 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.");
        }

        // 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.");
        }

        // 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"]);
        }

        // When you use foreach to enumerate dictionary elements,
        // the elements are retrieved as KeyValuePair objects.
        Console.WriteLine();
        foreach( KeyValuePair<string, string> kvp in openWith )
        {
            Console.WriteLine("Key = {0}, Value = {1}", 
                kvp.Key, kvp.Value);
        }

        // To get the values alone, use the Values property.
        SortedDictionary<string, string>.ValueCollection valueColl = 
            openWith.Values;

        // The elements of the ValueCollection are strongly typed
        // with the type that was specified for dictionary values.
        Console.WriteLine();
        foreach( string s in valueColl )
        {
            Console.WriteLine("Value = {0}", s);
        }

        // To get the keys alone, use the Keys property.
        SortedDictionary<string, string>.KeyCollection keyColl = 
            openWith.Keys;

        // The elements of the KeyCollection are strongly typed
        // with the type that was specified for dictionary keys.
        Console.WriteLine();
        foreach( string s in keyColl )
        {
            Console.WriteLine("Key = {0}", s);
        }

        // Use the Remove method to remove a key/value pair.
        Console.WriteLine("\nRemove(\"doc\")");
        openWith.Remove("doc");

        if (!openWith.ContainsKey("doc"))
        {
            Console.WriteLine("Key \"doc\" is not found.");
        }
    }
}

/* This code example produces the following output:

An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe

Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe
Key = rtf, Value = winword.exe
Key = txt, Value = notepad.exe

Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = hypertrm.exe
Value = winword.exe
Value = notepad.exe

Key = bmp
Key = dib
Key = doc
Key = ht
Key = rtf
Key = txt

Remove("doc")
Key "doc" is not found.
 */
Imports System.Collections.Generic

Public Class Example
    
    Public Shared Sub Main() 

        ' Create a new sorted dictionary of strings, with string 
        ' keys. 
        Dim openWith As New SortedDictionary(Of String, String)
        
        ' Add some elements to the dictionary. There are no 
        ' duplicate keys, but some of the values are duplicates.
        openWith.Add("txt", "notepad.exe")
        openWith.Add("bmp", "paint.exe")
        openWith.Add("dib", "paint.exe")
        openWith.Add("rtf", "wordpad.exe")
        
        ' The Add method throws an exception if the new key is 
        ' already in the dictionary.
        Try
            openWith.Add("txt", "winword.exe")
        Catch 
            Console.WriteLine("An element with Key = ""txt"" already exists.")
        End Try

        ' The Item property is the default property, so you 
        ' can omit its name when accessing elements. 
        Console.WriteLine("For key = ""rtf"", value = {0}.", _
            openWith("rtf"))
        
        ' The default Item property can be used to change the value
        ' associated with a key.
        openWith("rtf") = "winword.exe"
        Console.WriteLine("For key = ""rtf"", value = {0}.", _
            openWith("rtf"))
        
        ' If a key does not exist, setting the default Item property
        ' for that key adds a new key/value pair.
        openWith("doc") = "winword.exe"

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

        ' 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.
        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

        ' 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 you use foreach to enumerate dictionary elements,
        ' the elements are retrieved as KeyValuePair objects.
        Console.WriteLine()
        For Each kvp As KeyValuePair(Of String, String) In openWith
            Console.WriteLine("Key = {0}, Value = {1}", _
                kvp.Key, kvp.Value)
        Next kvp

        ' To get the values alone, use the Values property.
        Dim valueColl _
            As SortedDictionary(Of String, String).ValueCollection = _
            openWith.Values
        
        ' The elements of the ValueCollection are strongly typed
        ' with the type that was specified for dictionary values.
        Console.WriteLine()
        For Each s As String In valueColl 
            Console.WriteLine("Value = {0}", s)
        Next s

        ' To get the keys alone, use the Keys property.
        Dim keyColl _
            As SortedDictionary(Of String, String).KeyCollection = _
            openWith.Keys
        
        ' The elements of the KeyCollection are strongly typed
        ' with the type that was specified for dictionary keys.
        Console.WriteLine()
        For Each s As String In keyColl 
            Console.WriteLine("Key = {0}", s)
        Next s

        ' Use the Remove method to remove a key/value pair.
        Console.WriteLine(vbLf + "Remove(""doc"")")
        openWith.Remove("doc")
        
        If Not openWith.ContainsKey("doc") Then
            Console.WriteLine("Key ""doc"" is not found.")
        End If

    End Sub

End Class

' This code example produces the following output:
'
'An element with Key = "txt" already exists.
'For key = "rtf", value = wordpad.exe.
'For key = "rtf", value = winword.exe.
'Key = "tif" is not found.
'Key = "tif" is not found.
'Value added for key = "ht": hypertrm.exe
'
'Key = bmp, Value = paint.exe
'Key = dib, Value = paint.exe
'Key = doc, Value = winword.exe
'Key = ht, Value = hypertrm.exe
'Key = rtf, Value = winword.exe
'Key = txt, Value = notepad.exe
'
'Value = paint.exe
'Value = paint.exe
'Value = winword.exe
'Value = hypertrm.exe
'Value = winword.exe
'Value = notepad.exe
'
'Key = bmp
'Key = dib
'Key = doc
'Key = ht
'Key = rtf
'Key = txt
'
'Remove("doc")
'Key "doc" is not found.
' 

Remarks

The SortedDictionary<TKey,TValue> generic class is a binary search tree with O(log n) retrieval, where n is the number of elements in the dictionary. In this respect, it is similar to the SortedList<TKey,TValue> generic class. The two classes have similar object models, and both have O(log n) retrieval. Where the two classes differ is in memory use and speed of insertion and removal:

Each key/value pair can be retrieved as a KeyValuePair<TKey,TValue> structure, or as a DictionaryEntry through the nongeneric IDictionary interface.

Keys must be immutable as long as they are used as keys in the SortedDictionary<TKey,TValue>. Every key in a SortedDictionary<TKey,TValue> must be unique. A key cannot be null, but a value can be, if the value type TValue is a reference type.

SortedDictionary<TKey,TValue> requires a comparer implementation to perform key comparisons. You can specify an implementation of the IComparer<T> generic interface by using a constructor that accepts a comparer parameter; if you do not specify an implementation, the default genericcomparer Comparer<T>.Default is used. If type TKey implements the System.IComparable<T> generic interface, the default comparer uses that implementation.

The foreach statement of the C# language (for each in C++, For Each in Visual Basic) returns an object of the type of the elements in the collection. Since each element of the SortedDictionary<TKey,TValue> is a key/value pair, the element type is not the type of the key or the type of the value. Instead, the element type is KeyValuePair<TKey,TValue>. The following code shows C#, C++, and Visual Basic syntax.

for each(KeyValuePair<String^, String^> kvp in myDictionary)
{
    Console::WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}
foreach( KeyValuePair<string, string> kvp in myDictionary )
{
    Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}
For Each kvp As KeyValuePair(Of String, String) In myDictionary
    Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value)
Next kvp

The foreach statement is a wrapper around the enumerator, which allows only reading from the collection, not writing to it.

Constructors

SortedDictionary<TKey,TValue>()

Initializes a new instance of the SortedDictionary<TKey,TValue> class that is empty and uses the default IComparer<T> implementation for the key type.

SortedDictionary<TKey,TValue>(IComparer<TKey>)

Initializes a new instance of the SortedDictionary<TKey,TValue> class that is empty and uses the specified IComparer<T> implementation to compare keys.

SortedDictionary<TKey,TValue>(IDictionary<TKey,TValue>)

Initializes a new instance of the SortedDictionary<TKey,TValue> class that contains elements copied from the specified IDictionary<TKey,TValue> and uses the default IComparer<T> implementation for the key type.

SortedDictionary<TKey,TValue>(IDictionary<TKey,TValue>, IComparer<TKey>)

Initializes a new instance of the SortedDictionary<TKey,TValue> class that contains elements copied from the specified IDictionary<TKey,TValue> and uses the specified IComparer<T> implementation to compare keys.

Properties

Comparer

Gets the IComparer<T> used to order the elements of the SortedDictionary<TKey,TValue>.

Count

Gets the number of key/value pairs contained in the SortedDictionary<TKey,TValue>.

Item[TKey]

Gets or sets the value associated with the specified key.

Keys

Gets a collection containing the keys in the SortedDictionary<TKey,TValue>.

Values

Gets a collection containing the values in the SortedDictionary<TKey,TValue>.

Methods

Add(TKey, TValue)

Adds an element with the specified key and value into the SortedDictionary<TKey,TValue>.

Clear()

Removes all elements from the SortedDictionary<TKey,TValue>.

ContainsKey(TKey)

Determines whether the SortedDictionary<TKey,TValue> contains an element with the specified key.

ContainsValue(TValue)

Determines whether the SortedDictionary<TKey,TValue> contains an element with the specified value.

CopyTo(KeyValuePair<TKey,TValue>[], Int32)

Copies the elements of the SortedDictionary<TKey,TValue> to the specified array of KeyValuePair<TKey,TValue> structures, starting at the specified index.

Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetEnumerator()

Returns an enumerator that iterates through the SortedDictionary<TKey,TValue>.

GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
Remove(TKey)

Removes the element with the specified key from the SortedDictionary<TKey,TValue>.

ToString()

Returns a string that represents the current object.

(Inherited from Object)
TryGetValue(TKey, TValue)

Gets the value associated with the specified key.

Explicit Interface Implementations

ICollection.CopyTo(Array, Int32)

Copies the elements of the ICollection<T> to an array, starting at the specified array index.

ICollection.IsSynchronized

Gets a value indicating whether access to the ICollection is synchronized (thread safe).

ICollection.SyncRoot

Gets an object that can be used to synchronize access to the ICollection.

ICollection<KeyValuePair<TKey,TValue>>.Add(KeyValuePair<TKey,TValue>)

Adds an item to the ICollection<T>.

ICollection<KeyValuePair<TKey,TValue>>.Contains(KeyValuePair<TKey,TValue>)

Determines whether the ICollection<T> contains a specific key and value.

ICollection<KeyValuePair<TKey,TValue>>.IsReadOnly

Gets a value indicating whether the ICollection<T> is read-only.

ICollection<KeyValuePair<TKey,TValue>>.Remove(KeyValuePair<TKey,TValue>)

Removes the first occurrence of the specified element from the ICollection<T>.

IDictionary.Add(Object, Object)

Adds an element with the provided key and value to the IDictionary.

IDictionary.Contains(Object)

Determines whether the IDictionary contains an element with the specified key.

IDictionary.GetEnumerator()

Returns an IDictionaryEnumerator for the IDictionary.

IDictionary.IsFixedSize

Gets a value indicating whether the IDictionary has a fixed size.

IDictionary.IsReadOnly

Gets a value indicating whether the IDictionary is read-only.

IDictionary.Item[Object]

Gets or sets the element with the specified key.

IDictionary.Keys

Gets an ICollection containing the keys of the IDictionary.

IDictionary.Remove(Object)

Removes the element with the specified key from the IDictionary.

IDictionary.Values

Gets an ICollection containing the values in the IDictionary.

IDictionary<TKey,TValue>.Keys

Gets an ICollection<T> containing the keys of the IDictionary<TKey,TValue>.

IDictionary<TKey,TValue>.Values

Gets an ICollection<T> containing the values in the IDictionary<TKey,TValue>.

IEnumerable.GetEnumerator()

Returns an enumerator that iterates through the collection.

IEnumerable<KeyValuePair<TKey,TValue>>.GetEnumerator()

Returns an enumerator that iterates through a collection.

IReadOnlyDictionary<TKey,TValue>.Keys

Gets a collection containing the keys in the SortedDictionary<TKey,TValue>.

IReadOnlyDictionary<TKey,TValue>.Values

Gets a collection containing the values in the SortedDictionary<TKey,TValue>.

Extension Methods

GetValueOrDefault<TKey,TValue>(IReadOnlyDictionary<TKey,TValue>, TKey)

Tries to get the value associated with the specified key in the dictionary.

GetValueOrDefault<TKey,TValue>(IReadOnlyDictionary<TKey,TValue>, TKey, TValue)

Tries to get the value associated with the specified key in the dictionary.

Remove<TKey,TValue>(IDictionary<TKey,TValue>, TKey, TValue)

Tries to remove the value with the specified key from the dictionary.

TryAdd<TKey,TValue>(IDictionary<TKey,TValue>, TKey, TValue)

Tries to add the specified key and value to the dictionary.

CopyToDataTable<T>(IEnumerable<T>)

Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)

Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)

Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

Cast<TResult>(IEnumerable)

Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable)

Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable)

Enables parallelization of a query.

AsQueryable(IEnumerable)

Converts an IEnumerable to an IQueryable.

Ancestors<T>(IEnumerable<T>)

Returns a collection of elements that contains the ancestors of every node in the source collection.

Ancestors<T>(IEnumerable<T>, XName)

Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.

DescendantNodes<T>(IEnumerable<T>)

Returns a collection of the descendant nodes of every document and element in the source collection.

Descendants<T>(IEnumerable<T>)

Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

Descendants<T>(IEnumerable<T>, XName)

Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

Elements<T>(IEnumerable<T>)

Returns a collection of the child elements of every element and document in the source collection.

Elements<T>(IEnumerable<T>, XName)

Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

InDocumentOrder<T>(IEnumerable<T>)

Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.

Nodes<T>(IEnumerable<T>)

Returns a collection of the child nodes of every document and element in the source collection.

Remove<T>(IEnumerable<T>)

Removes every node in the source collection from its parent node.

Applies to

Thread Safety

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

A SortedDictionary<TKey,TValue> can support multiple readers concurrently, as long as the collection is not modified. Even so, enumerating through a collection is intrinsically not a thread-safe procedure. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

See also