Dictionary<TKey,TValue>.Add() Method is used to add a specified key and value to the dictionary.
Syntax:
public void Add (TKey key, TValue value);
Parameters:
key: It is the key of the element to add.
value: It is the value of the element to add. The value can be null for reference types.
Exceptions:
- ArgumentNullException : If the key is null.
- ArgumentException : If an element with the same key already exists in the Dictionary.
Below are the programs to illustrate the use of Dictionary<TKey,TValue>.Add() Method:
Example 1:
// C# code to add the specified key // and value into the Dictionary using System;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Create a new dictionary
// of strings, with string keys.
Dictionary< string , string > myDict =
new Dictionary< string , string >();
// Adding key/value pairs in myDict
myDict.Add( "Australia" , "Canberra" );
myDict.Add( "Belgium" , "Brussels" );
myDict.Add( "Netherlands" , "Amsterdam" );
myDict.Add( "China" , "Beijing" );
myDict.Add( "Russia" , "Moscow" );
myDict.Add( "India" , "New Delhi" );
// To get count of key/value
// pairs in myDict
Console.WriteLine( "Total key/value pairs in" +
" myDict are : " + myDict.Count);
// Displaying the key/value
// pairs in myDict
Console.WriteLine( "The key/value pairs" +
" in myDict are : " );
foreach (KeyValuePair< string , string > kvp in myDict)
{
Console.WriteLine( "Key = {0}, Value = {1}" ,
kvp.Key, kvp.Value);
}
}
} |
Output:
Total key/value pairs in myDict are : 6 The key/value pairs in myDict are : Key = Australia, Value = Canberra Key = Belgium, Value = Brussels Key = Netherlands, Value = Amsterdam Key = China, Value = Beijing Key = Russia, Value = Moscow Key = India, Value = New Delhi
Example 2:
// C# code to add the specified // key and value into the Dictionary using System;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Create a new dictionary of
// strings, with string keys.
Dictionary< string , string > myDict =
new Dictionary< string , string >();
// Adding key/value pairs in myDict
myDict.Add( "Australia" , "Canberra" );
myDict.Add( "Belgium" , "Brussels" );
myDict.Add( "Netherlands" , "Amsterdam" );
myDict.Add( "China" , "Beijing" );
myDict.Add( "Russia" , "Moscow" );
myDict.Add( "India" , "New Delhi" );
// The Add method throws an
// exception if the new key is
// already in the dictionary.
try {
myDict.Add( "Russia" , "Moscow" );
}
catch (ArgumentException) {
Console.WriteLine( "An element with Key " +
"= \"Russia\" already exists." );
}
}
} |
Output:
An element with Key = "Russia" already exists.
Note:
- A key cannot be null, but a value can be if TValue is a reference type.
- If Count is less than the capacity, this method approaches an O(1) operation.
- If the capacity must be increased to accommodate the new element, this method becomes an O(n) operation, where n is Count.
Reference: