The Hashtable object contains items in key/value pairs. The keys are used as indexes. We can search value by using their corresponding key.
In .NET, the class that implements a hash table is the Hashtable class.
By using Add Method we can add elements to the Hashtable as shown below:
private Hashtable table = new Hashtable();
public void AddEntry(BookEntry entry)
{
table.Add( entry.GetPerson(), entry );
}
Once the Hashtable gets populated,you can search and retrieve data in it by calling the indexer for the Hashtable class as shown below:
public BookEntry GetEntry(Person key)
{
return (BookEntry) table[key];
}
You can also remove the records from the Hashtable by calling the Remove Method which takes a key identifying the element you want to remove as shown below:
public void DeleteEntry(Person key)
{
table.Remove( key );
}
The data populated from the Hashtable can be saved using Serialization process.
Serialization is a process where the object gets converted into a linear sequence of Bytes for storage or transmission to another location.
This process can be done by using BinaryFormater class which serializes Hashtable object to file stream.
public void Save()
{
Stream s = File.Open("Phone.bin", FileMode.Create, FileAccess.ReadWrite);
BinaryFormatter b = new BinaryFormatter();
b.Serialize(s, table);
s.Close();
}
By using the Deserialize method, you can get back the recovered Hashtable object as shown below:
s = File.Open("Phone.bin", FileMode.Open, FileAccess.Read);
BinaryFormatter b = new BinaryFormatter();
table = (Hashtable) b.Deserialize(s);