C# | Creating a synchronized (thread-safe) wrapper for the Hashtable

Hashtable.Synchronized(Hashtable) Method is used to return a synchronized (thread-safe) wrapper for the Hashtable.
Syntax:

public static System.Collections.Hashtable Synchronized (System.Collections.Hashtable table);

Here table is the Hashtable which is to be synchronized.
Return Value: This method returns a synchronized (thread-safe) wrapper for the Hashtable.
Exception: This method will throw the ArgumentNullException if the table is null. 
Below programs illustrate the use of above-discussed method:
Example 1:

Output: 
 

has1 Hashtable is not synchronized.
has2 Hashtable is synchronized.

Example 2:

Runtime Error:
 

Unhandled Exception: 
System.ArgumentNullException: Value cannot be null. 
Parameter name: table 
 

Note:

• This method is a thread-safe for multiple readers and writers. Furthermore, the synchronized wrapper ensures that there is only one writer writing at a time.
• Enumerating through a collection is intrinsically not a thread-safe process. Other threads can still modify the collection, which causes the enumerator to throw an exception even when a collection is synchronized.
• To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.
• This method is an O(1) operation.

Reference: 

• https://learn.microsoft.com/en-us/dotnet/api/system.collections.hashtable.synchronized?view=netframework-4.7.2