Hashtable in c#

The Hashtable class in C# represents a hashtable. The following code creates a Hashtable:

private Hashtable hshTable = new Hashtable();

Adding Items to a Hashtable

Add method of Hashtable is used to add items to the hashtable. The method has index and value parameters. The following code adds three items to hashtable.

hshTable .Add("Author1", "Mahesh Chand");
hshTable .Add("Author2", "James Brand");
hshTable .Add("Author3", "Mike Gold");


Retrieving an Item Value from Hashtable

The following code returns the value of "Author1" key:

string name = hshTable["Author1"].ToString();

Removing Items from a Hashtable

The Remove method removes an item from a Hashtable. The following code removes item with index "Author1" from the hashtable:

hshTable.Remove("Author1");

Looking through all Items of a Hashtable

The following code loops through all items of a hashtable and reads the values.

// Loop through all items of a Hashtable
IDictionaryEnumerator en = hshTable.GetEnumerator();
while (en.MoveNext())
{
string str = en.Value.ToString();
}

Using Foreach loop -

foreach (DictionaryEntry entry in hshTable)
{
Response.Write(entry.Key);
Response.Write(entry.Value);
}

Generic List in C#

Using a Generic List in C# is an efficient method of storing a collection of variables. And probably the best part is that the List is strongly typed and casting (which degrades performance) will no longer be necessary. Your collection of variables should be of the same data type. Generic Lists were first introduced into the .NET Framework 2.0. Before we begin our Generic List example, first remember to include the correct namespace below:

using System.Collections.Generic;

In our example, we will store the integers 5, 8, 435, 76, 3256, and -85. Our next step is to initialize a List using Generics. Because we are storing integers, our it with be an int Generics List. If you wish to create the List as another variable type, simply replace int with double, decimal, string, or another type of element. We will give our List the name myGenericIntegerList.

ListmyGenericIntegerList = new List();

Now that the List has been created and initialized, we easily add integer elements. Since we stated this list as an int, the input will now be strongly typed to only accept integer values. We will now add the integeres5, 8, 435, 76, 3256, and -85 iin the example below:

myGenericIntegerList.Add(5);
myGenericIntegerList.Add(8);
myGenericIntegerList.Add(435);
myGenericIntegerList.Add(76);
myGenericIntegerList.Add(3256);
myGenericIntegerList.Add(-85);

Your generic int List is now complete! Another advantage to using the generics List is there are helper functions such as average, contains, and counts, and toArray. As brought up by Khalid, the average function is an extension method.

double average = myGenericIntegerList.Average();
bool contains = myGenericIntegerList.Contains(4);
int count = myGenericIntegerList.Count;
int[] intArray = myGenericIntegerList.ToArray();

You can print it out like -
Response.Write(myGenericIntegerList[1]);

For more functions, you can either visit the MSDN and search for “List(T) Methods” or better just give the function a try in Visual Studio and let Intellisense show you other functions.