An item that is part of a list is called datum, with the plural being data, but data can also be used for singular. The group of items, or data, that makes up a list is referred to as a set of data.

To support the creation and management of a set of data, the .NET Framework provides the DataSet class, which is defined in the System.Data namespace. Therefore, to create a list, you can start by declaring a variable of type DataSet. To initialize a DataSet variable, the class is equipped with four constructors, the first of which is the default, meaning it doesn't take any argument. The DataSet default constructor allows you to declare a variable without providing further information, just to let the compiler know that you are going to create or need a list of items. Here is an example:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            DataSet dsVideoCollection = new DataSet();
        }
    }
}

If you are planning to use a DataSet object from more than one method or event, you can declare it globally, that is, in the class of a form. Here is an example:

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            dsVideoCollection = new DataSet();
        }
    }
}

To visually assist you with creating a data set, in its Data section, the Toolbox provides the DataSet object. Therefore, to visually start creating a data set, you can click DataSet and click the form. When you do this, the Add Dataset dialog box would come up. You must click the Untyped Dataset radio button:

Then click OK. After doing it, the compiler would programmatically declare a variable and give its name in the (Name) field of the Properties window.

When creating a set of data, you must name it. This would allow you to refer to the set later on by a formal name. If you create a data set using the DataSet's default constructor, the compiler would give it a default name. 

To support the data set's object name, the DataSet class is equipped with a property named DataSetName. Therefore, if you create a data set using the class's default constructor, to give it a name, you can assign a string to the DataSetName property. If you visually create a data set, the Microsoft Visual Studio would create a default name for it in the DataSetName field of the Properties Windows. If you want to change that name, replace that property's value.

To specify a data set's name when creating it, you can use the following constructor of the DataSet class:

public DataSet(string dataSetName);

This constructor takes as argument the formal name of the set. The name can be anything but it must respect the rules of names of the C# language. Here is an example:

using System;
using System.Data;

public class VideoCollection
{
    public DataSet dsVideoCollection;

    public VideoCollection()
    {
        dsVideoCollection = new DataSet("Videos");
    }
}

Imagine you have a list of movie directors and you want to group their names into a list. Here is an example:

Rob Reiner, Jonathan Lynn, Bruce Beresford, Jonathan Demme, Adrian Lyne

This is a one-dimensional list like a simple array. While working on this list, you may decide to create a video collection and make the above items into a formal list. A typical movie provides such information as its length, its rating, the year it was released, etc. To create such a list, you would group items by categories. One category may contain the titles of the videos. Another category may contain the names of the directors, and so on.

To better organize a list, you may create each category, then enter the value of each category that corresponds to a particular video. Here is an example:

This type of list is called a table: A table is a two-dimensional list that contains one or different categories of items and each category is represented with a particular value. A category of values is called a column. Under each category, you may have a group of values that belong to the same entry. Such a group of values is called a row or a record. In the above table, the values "A Few Good Men", "Rob Reiner", "1992", "138 Minute", "VH", and "R" constitute one row or record.

In our introduction, we defined a data set as one or more lists considered in a single group. Reversely, one or more lists grouped in a single entity is called a data set. In such a scenario, each list is created as a table, made of categories of values. Put in reverse, a data set is one or more tables used in one database.

To support the creation and management of a table, the .NET Framework provides the DataTable class that is defined in the System.Data namespace. There are various ways you can create a table. You can declare a variable of type DataTable. To initialize the variable, the DataTable class is equipped with four constructors. The default constructor allows you to create a table without giving more details, especially without formally naming it. Here is an example:

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            dsVideoCollection = new DataSet("Videos");

            DataTable tblDirectors = new DataTable();
        }
    }
}

If you are planning to refer to the table from more than one method, you should declare it globally. Here is an example:

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataSet dsVideoCollection;
        DataTable tblDirectors;

        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            dsVideoCollection = new DataSet("Videos");

            tblDirectors = new DataTable();
        }
    }
}

When creating a table, you must name it; that is, you must give it an object name. To support the name of a table, the DataTable class is equipped with a property named TableName. To specify the name of a table, you can assign a string to it. Here is an example:

private void btnDocument_Click(object sender, EventArgs e)
{
    dsVideoCollection = new DataSet("Videos");

    tblDirectors = new DataTable();
    tblDirectors.TableName = "Directors";
}

To specify the name of a table when creating it, you can use the following constructor of the DataTable class:

public DataTable(string tableName);

This constructor expects as argument a string that would constitute the object name of the table. Here is an example:

public partial class Exercise : Form
{
    DataSet dsVideoCollection;
    DataTable tblDirectors;
    DataTable tblVideoCategories;

    public Exercise()
    {
        InitializeComponent();
    }

    private void btnDocument_Click(object sender, EventArgs e)
    {
        dsVideoCollection = new DataSet("Videos");

        tblDirectors = new DataTable();
        tblDirectors.TableName = "Directors";

        tblVideoCategories = new DataTable("Categories");
    }
}

After creating a table, you can add it to a DataSet object.

To visually create a table, under the form, you can click the data set object. In the Properties window, you can click Tables and click the ellipsis button of its field. This would open the Table Collection Editor. To create a table, you can click the Add button. A table would be added:

The new table has a default variable name under Members and an object name. To change the variable name, under the Properties list, you can click (Name) and type the desired name. To change the object name, you can click TableName and type the new name.

The tables that belong to a DataSet object are stored in a property called Tables. The DataSet.Tables property is an object of type DataTableCollection. The DataTableCollection class is derived from a class named InternalDataCollectionBase. DataTableCollection is a class that provides everything you need to add, locate, or manage any table that belongs to a DataSet object.

While performing an operation such as adding a new table to the collection, the DataTableCollection class fires a CollectionChanging event. The syntax of this event is:

public event CollectionChangeEventHandler CollectionChanging

You cannot visually generate this event in Microsoft Visual Studio. If you want to catch it, you must manually define it. Here is an example:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataTable tblDirectors;
        DataTable tblVideoCategories;
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();

            dsVideoCollection = new DataSet("Videos");

            dsVideoCollection.Tables.CollectionChanged +=
                new CollectionChangeEventHandler(TableCollectionHasChanged);
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            dsVideoCollection = new DataSet("Videos");

            tblDirectors = new DataTable();
            tblDirectors.TableName = "Directors";

            tblVideoCategories = new DataTable("Categories");
        }

        void TableCollectionHasChanged(object sender, CollectionChangeEventArgs e)
        {
            MessageBox.Show("The list of tables has been changed");
        }
    }
}

As you can see, this event is based on the CollectionChangeEventArgs class. The CollectionChangeEventArgs class has two properties. The Action property specifies what happened to the collection. This property is of type CollectionChangeAction, which is an enumeration. If a new table is being added, then the action is Add.

The CollectionChangeEventArgs class is also equipped with a property named Element, which is of type object. This property holds a DataTableCollection object with the current changes.

Using the DataSet.Tables property, to add a created table to a DataSet object, call one of the Add() methods of the DataTableCollection class. The first version of this method has the following syntax:

public virtual DataTable Add();

This method can be used to add a new table that uses the default name. Here is an example:

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataTable tblRatings;
        DataTable tblDirectors;
        DataTable tblVideoCategories;
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            dsVideoCollection = new DataSet("Videos");

            tblDirectors = new DataTable();
            tblDirectors.TableName = "Directors";
            tblVideoCategories = new DataTable("Categories");

            tblRatings = dsVideoCollection.Tables.Add();
        }
    }
}

If this is the first table added to the collection, it would be named Table1. The second version of the DataTableCollection.Add() method uses the following syntax:

public virtual void Add(DataTable table);

This version allows you to add a predefined or declared DataTable object. Here is an example:

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataTable tblRatings;
        DataTable tblDirectors;
        DataTable tblVideoCategories;
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            dsVideoCollection = new DataSet("Videos");

            tblDirectors = new DataTable();
            tblDirectors.TableName = "Directors";
            dsVideoCollection.Tables.Add(tblDirectors);

            tblVideoCategories = new DataTable("Categories");
            dsVideoCollection.Tables.Add(tblVideoCategories);

            tblRatings = dsVideoCollection.Tables.Add();
        }
    }
}

This second version of the method requires that you create a DataTable object first and the table probably has a name. Alternatively, if you want to add a table using its formal name, you can use the third version of this method. Its syntax is:

public virtual DataTable Add(string name);

This version works like the first except that, instead of the default name (such as Table1, Table2, etc), it lets you specify the desired name of the new table. Here are examples:

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataTable tblActors;
        DataTable tblFormats;
        DataTable tblRatings;
        DataTable tblDirectors;
        DataTable tblVideoCategories;
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            dsVideoCollection = new DataSet("Videos");

            tblDirectors = new DataTable();
            tblDirectors.TableName = "Directors";
            dsVideoCollection.Tables.Add(tblDirectors);

            tblVideoCategories = new DataTable("Categories");
            dsVideoCollection.Tables.Add(tblVideoCategories);

            tblRatings = dsVideoCollection.Tables.Add();

            tblActors = dsVideoCollection.Tables.Add("Actors");
            tblFormats = dsVideoCollection.Tables.Add("Formats");
        }
    }
}

When a new table has been created, the DataTableCollection class fires a CollectionChanged event. The syntax of this event is:

public event CollectionChangeEventHandler CollectionChanged;

Once again, you cannot visually generate this event. Instead, if you want to catch it, you must manually define it. Here is an example:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();

            dsVideoCollection = new DataSet("Videos");

            dsVideoCollection.Tables.CollectionChanged +=
                new CollectionChangeEventHandler(TableCollectionHasChanged);
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
        }

        void TableCollectionHasChanged(object sender, CollectionChangeEventArgs e)
        {
        }
    }
}

This event fires every time a new table is added to the collection. Here is an example:

namespace VideoCollection1
{
    public partial class Exercise : Form
    {
        DataTable tblActors;
        DataTable tblFormats;
        DataTable tblRatings;
        DataTable tblDirectors;
        DataTable tblVideoCategories;
        DataSet dsVideoCollection;

        public Exercise()
        {
            InitializeComponent();

            dsVideoCollection = new DataSet("Videos");

            dsVideoCollection.Tables.CollectionChanged +=
                new CollectionChangeEventHandler(TableCollectionHasChanged);
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            tblDirectors = new DataTable();
            tblDirectors.TableName = "Directors";
            dsVideoCollection.Tables.Add(tblDirectors);

            tblVideoCategories = new DataTable("Categories");
            dsVideoCollection.Tables.Add(tblVideoCategories);

            tblRatings = dsVideoCollection.Tables.Add();

            tblActors = dsVideoCollection.Tables.Add("Actors");
            tblFormats = dsVideoCollection.Tables.Add("Formats");

            foreach (DataTable tbl in dsVideoCollection.Tables)
                lbxVideos.Items.Add(tbl.TableName);
        }

        void TableCollectionHasChanged(object sender, CollectionChangeEventArgs e)
        {
            MessageBox.Show("The list of tables has been changed");
        }

    }
}

This event also is based on the CollectionChangeEventArgs class. If a new table was added, then the action of the event is Add.

Instead of adding one table at a time, you can create a list of tables and then add it to the DataSet.Tables collection. To support this operation, the DataTableCollection is equipped with the AddRange() method. Its syntax is:

public void AddRange(DataTable[] tables);

This method expects an array of DataTable objects as argument. Here is an example:

namespace BookCollection1
{
    public partial class Exercise : Form
    {
        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            DataSet dsBooks = new DataSet("Book");

            DataTable dtCategories = new DataTable("Categorie");
            DataTable dtAuthors = new DataTable("Author");
            DataTable dtPublishers = new DataTable("Publisher");
            DataTable dtBooks = new DataTable("Book");

            DataTable[] colTables =
		{ dtCategories, dtAuthors, dtPublishers, dtBooks };
            dsBooks.Tables.AddRange(colTables);
        }
    }
}