C# | Adding an element into the Hashtable
Last Updated :
11 Jul, 2025
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The Hashtable class represents a collection of key-and-value pairs that are organized based on the hash code of the key. The key is used to access the items in the collection. Hashtable.Add(Object, Object) Method is used to adds an element with the specified key and value into the Hashtable.
Syntax:
CSHARP
CSHARP
public virtual void Add(object key, object value);Parameters:
key: It is the specified key of the element to add of type System.Object. value: It is the specified value of the element to add of type System.Object. The value can be null.Exceptions:
- ArgumentNullException : If the key is null.
- ArgumentException : If an element with the same key already exists in the Hashtable.
- NotSupportedException : Either Hashtable is read-only or Hashtable has a fixed size.
// C# code for adding an element with the
// specified key and value into the Hashtable
using System;
using System.Collections;
class GFG {
// Driver code
public static void Main()
{
// Creating a Hashtable
Hashtable myTable = new Hashtable();
// Adding elements in Hashtable
myTable.Add("g", "geeks");
myTable.Add("c", "c++");
myTable.Add("d", "data structures");
myTable.Add("q", "quiz");
// Get a collection of the keys.
ICollection c = myTable.Keys;
// Displaying the contents
foreach(string str in c)
Console.WriteLine(str + ": " + myTable[str]);
}
}
// C# code for adding an element with the// specified key and value into the Hashtableusing System;using System.Collections;class GFG { // Driver code public static void Main() { // Creating a Hashtable Hashtable myTable = new Hashtable(); // Adding elements in Hashtable myTable.Add("g", "geeks"); myTable.Add("c", "c++"); myTable.Add("d", "data structures"); myTable.Add("q", "quiz"); // Get a collection of the keys. ICollection c = myTable.Keys; // Displaying the contents foreach(string str in c) Console.WriteLine(str + ": " + myTable[str]); }}
Output:
Example 2:
d: data structures c: c++ q: quiz g: geeks
// C# code for adding an element with the
// specified key and value into the Hashtable
using System;
using System.Collections;
class GFG {
// Driver code
public static void Main()
{
// Creating a Hashtable
Hashtable myTable = new Hashtable();
// Adding elements in Hashtable
myTable.Add("4", "Even");
myTable.Add("9", "Odd");
myTable.Add("5", "Odd and Prime");
myTable.Add("2", "Even and Prime");
// Get a collection of the keys.
ICollection c = myTable.Keys;
// Displaying the contents
foreach(string str in c)
Console.WriteLine(str + ": " + myTable[str]);
}
}
// C# code for adding an element with the// specified key and value into the Hashtableusing System;using System.Collections;class GFG { // Driver code public static void Main() { // Creating a Hashtable Hashtable myTable = new Hashtable(); // Adding elements in Hashtable myTable.Add("4", "Even"); myTable.Add("9", "Odd"); myTable.Add("5", "Odd and Prime"); myTable.Add("2", "Even and Prime"); // Get a collection of the keys. ICollection c = myTable.Keys; // Displaying the contents foreach(string str in c) Console.WriteLine(str + ": " + myTable[str]); }}
Output:
Reference:
5: Odd and Prime 9: Odd 2: Even and Prime 4: Even
