What is difference between dictionary and hashtable in c#?| Difference between dictionary and hashtable in c#| dictionary in c#| hashtable in c#

What is difference between dictionary and hashtable in c#?

 Both `Dictionary` and `Hashtable` are used to store key-value pairs in C# and offer similar functionality, but there are some important differences between them.

Here are the main differences between `Dictionary` and `Hashtable` in C#:

1. Type safety: `Dictionary` is a generic class, which means that you can specify the types of the keys and values when you create an instance of the class. This provides compile-time type safety and avoids the need for casting. On the other hand, `Hashtable` is not type-safe, which means that you need to cast the keys and values to the correct types at runtime.

2. Performance: `Hashtable` is an older data structure that was introduced in .NET 1.0 and is implemented using a hash table. It provides efficient O(1) access to elements by key, but can have slower performance than `Dictionary` for small data sets and has higher memory overhead. `Dictionary` is a newer data structure that was introduced in .NET 2.0 and is implemented using a hash table or a binary tree, depending on the size of the data set. It provides similar O(1) access to elements by key, but has better performance and memory usage for small data sets.

3. Thread safety: `Hashtable` is thread-safe for read-only operations, but not for write operations. To synchronize access to a `Hashtable` instance, you need to use a lock or other synchronization mechanism. On the other hand, `Dictionary` is not thread-safe by default, but you can use the `ConcurrentDictionary` class or other synchronization mechanisms to make it thread-safe.

4. Null values: `Dictionary` allows null values for both keys and values, while `Hashtable` does not allow null keys or values.

In general, if you need type safety, good performance, and thread safety in your key-value storage, you should use `Dictionary`. If you need backward compatibility with older .NET versions or don't care about type safety or thread safety, you can use `Hashtable`.