C# StringDictionary Class
Last Updated :
06 Feb, 2025
In C#, the StringDictionary class is the part of the System.Collections.Specialized namespace. It is a collection of key-value pairs where the keys are strings and values are objects. It is similar to a Hashtable. But it is specifically designed for use with string keys.
- Keys are always strings, and values can be any object.
- It does not maintain the order of insertion of elements.
- Provides indexed access to values based on string keys.
- By default, it is case-sensitive.
Example: This example demonstrates how to use the StringDictionary class to store and iterate over key-value pairs where keys are strings and values can be any object.
C#
// C# program to demonstrate StringDictionary class
using System;
using System.Collections;
using System.Collections.Specialized;
class Geeks
{
static void Main()
{
// Create a StringDictionary
StringDictionary sd = new StringDictionary();
// Insert key-value pairs
sd.Add("1", "Geek1");
sd.Add("2", "Geek2");
sd.Add("3", "Geek3");
sd.Add("4", "Geek4");
// Iterate through the StringDictionary
// and print the key-value pairs
foreach (DictionaryEntry i in sd)
{
Console.WriteLine($"{i.Key} --> {i.Value}");
}
}
}
Output3 --> Geek3
4 --> Geek4
2 --> Geek2
1 --> Geek1
Declaration of StringDictionary
In C#, the StringDictionary is declared as:
StringDictionary dictionary = new StringDictionary();
Constructor
StringDictionary(): Initializes a new instance of the StringDictionary class.
Example: This example demonstrates how to create a StringDictionary, add integer values as string, and iterate through the dictionary to display the keys and their corresponding values.
C#
// C# program to demonstrates how to
// create a StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
class Geeks {
public static void Main()
{
// Creating a StringDictionary
StringDictionary sd = new StringDictionary();
// Adding key and value into the StringDictionary
sd.Add("X", "100");
sd.Add("Y", "200");
sd.Add("Z", "300");
// Displaying the keys and values in StringDictionary
foreach(DictionaryEntry i in sd)
{
Console.WriteLine(i.Key + " --> " + i.Value);
}
}
}
Outputx --> 100
z --> 300
y --> 200
Properties
| Properties | Description |
|---|
| Count | Gets the number of key/value pairs in the StringDictionary. |
| IsSynchronized | Gets a value indicating whether access to the StringDictionary is synchronized (thread safe). |
| Item[String] | Gets or sets the value associated with the specified key. |
| Keys | Gets a collection of keys in the StringDictionary. |
| SyncRoot | Gets an object that can be used to synchronize access to the StringDictionary. |
| Values | Gets a collection of values in the StringDictionary. |
Example: This example demonstrates how to use Values property to access that values in StringDictionary and check its IsSynchronized property to determine if its thread-safe.
C#
// C# program to demonstrates the working of
// values and IsSynchronized property
using System;
using System.Collections;
using System.Collections.Specialized;
class Geeks{
public static void Main() {
// Creating a StringDictionary
StringDictionary sd = new StringDictionary();
// Adding key and value
sd.Add("1", "One");
sd.Add("5", "Five");
sd.Add("7", "Seven");
sd.Add("10", "Ten");
// Values Property
// Getting a collection of values in the StringDictionary
foreach (string i in sd.Values) {
Console.WriteLine(i);
}
// IsSynchronized Property
// Checking if StringDictionary is synchronized(thread-safe)
Console.WriteLine(sd.IsSynchronized);
}
}
OutputFive
Seven
Ten
One
False
Methods
| Methods | Description |
|---|
| Add(String, String) | Adds an entry with the specified key and value into the StringDictionary. |
| Clear() | Removes all entries from the StringDictionary. |
| ContainsKey(String) | Determines if the StringDictionary contains a specific key. |
| ContainsValue(String) | Determines if the StringDictionary contains a specific value. |
| CopyTo(Array, Int32) | Copies the string dictionary values to a one-dimensional Array instance at the specified index. |
| Equals(Object) | Determines whether the specified object is equal to the current object. |
| GetEnumerator() | Returns an enumerator that iterates through the string dictionary. |
| GetHashCode() | Serves as the default hash function. |
| GetType() | Gets the Type of the current instance. |
| MemberwiseClone() | Creates a shallow copy of the current Object. |
| Remove(String) | Removes the entry with the specified key from the string dictionary. |
| ToString() | Returns a string that represents the current object. |
Example 1: This example demonstrates how to use the Count property to get the number of key-value pairs and how to remove key-value pair using the Remove() method.
C#
// C# code to remove the entry
// with the specified key from
// the StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
class Geeks {
public static void Main()
{
// Creating a StringDictionary
StringDictionary sd = new StringDictionary();
// Adding key and value into the StringDictionary
sd.Add("X", "100");
sd.Add("Y", "200");
sd.Add("Z", "300");
// Displaying the keys and values in StringDictionary
Console.WriteLine("The number of key-value pairs are : " + sd.Count);
// Removing the entry with the specified
// key from the StringDictionary
sd.Remove("Y");
// Displaying the keys and values in StringDictionary
Console.WriteLine("The number of key-value pairs are : " + sd.Count);
}
}
OutputThe number of key-value pairs are : 3
The number of key-value pairs are : 2
Example 2: This example demonstrates how to use the CopyTo method to copy the contents of a StringDicitonary into an array and then display the key-value pairs from the array.
C#
// C# code to copy StringDictionary
// to Array at the specified index
using System;
using System.Collections;
using System.Collections.Specialized;
class Geeks {
public static void Main()
{
// Creating a StringDictionary
StringDictionary sd = new StringDictionary();
// Adding key and value into the StringDictionary
sd.Add("1", "Geeks");
sd.Add("2", "for");
sd.Add("3", "Geeks");
// Creating an Array
DictionaryEntry[] arr = { new DictionaryEntry(),
new DictionaryEntry(),
new DictionaryEntry() };
// Copying StringDictionary to
// Array at the specified index
sd.CopyTo(arr, 0);
// Displaying key and value pairs in Array
for (int i = 0; i < arr.Length; i++) {
Console.WriteLine(arr[i].Key + " --> "
+ arr[i].Value);
}
}
}
Output3 --> Geeks
2 --> for
1 --> Geeks
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