System.DataTable Class

Overview

Syntax

Properties

Methods

Events

Example

The System.DataTable class represents an in‑memory table of data. It can be used on its own or as part of a DataSet. A DataTable contains a collection of DataColumn, DataRow, and optional constraints.

Typical scenarios include reading data from a database, editing it offline, and then updating the source.

public class DataTable : MarshalByValueComponent, ISerializable, IListSource, ISupportInitialize, IDbDataAdapter, IXmlSerializable

Key Properties

Property	Type	Description
`Columns`	`DataColumnCollection`	Gets the collection of columns that belong to this table.
`Rows`	`DataRowCollection`	Gets the collection of rows that belong to this table.
`PrimaryKey`	`DataColumn[]`	Gets or sets an array of columns that function as primary key for the table.
`TableName`	`string`	Gets or sets the name of the table.
`Constraints`	`ConstraintCollection`	Gets the collection of constraints (e.g., foreign keys) for the table.
`Namespace`	`string`	Gets or sets the namespace for the XML representation of the table.

Important Methods

Method	Signature	Description
`NewRow`	`DataRow NewRow()`	Creates a new `DataRow` with the same schema as the table.
`Rows.Add`	`DataRow Add(DataRow row)`	Adds a `DataRow` to the table.
`AcceptChanges`	`void AcceptChanges()`	Commits all the changes made to the table since the last time `AcceptChanges` was called.
`RejectChanges`	`void RejectChanges()`	Rolls back all changes that have been made to the table since it was loaded or `AcceptChanges` was last called.
`Select`	`DataRow[] Select(string filterExpression, string sort, DataViewRowState recordStates)`	Filters rows based on a criteria string.
`Merge`	`void Merge(DataTable table, bool preserveChanges, MissingSchemaAction missingSchemaAction)`	Merges the specified table with the current instance.
`ReadXml`	`void ReadXml(string fileName)`	Populates the table from an XML file.
`WriteXml`	`void WriteXml(string fileName)`	Writes the table's content to an XML file.

Relevant Events

Event	Delegate	Description
`RowChanged`	`DataRowChangeEventHandler`	Occurs after a row has been changed successfully.
`RowChanging`	`DataRowChangeEventHandler`	Occurs before a row change is committed.
`RowDeleted`	`DataRowChangeEventHandler`	Occurs after a row is deleted.
`RowDeleting`	`DataRowChangeEventHandler`	Occurs before a row is deleted.
`ColumnChanged`	`DataColumnChangeEventHandler`	Occurs after a column value is changed.
`ColumnChanging`	`DataColumnChangeEventHandler`	Occurs before a column value is changed.

Example: Creating and Using a DataTable

using System;
using System.Data;

class Program
{
    static void Main()
    {
        // Create a new DataTable.
        DataTable table = new DataTable("Products");

        // Define columns.
        DataColumn idColumn = new DataColumn("ProductID", typeof(int));
        idColumn.AutoIncrement = true;
        idColumn.AutoIncrementSeed = 1;
        idColumn.Unique = true;

        DataColumn nameColumn = new DataColumn("ProductName", typeof(string));
        DataColumn priceColumn = new DataColumn("Price", typeof(decimal));

        table.Columns.Add(idColumn);
        table.Columns.Add(nameColumn);
        table.Columns.Add(priceColumn);

        // Set primary key.
        table.PrimaryKey = new DataColumn[] { idColumn };

        // Add rows.
        DataRow row = table.NewRow();
        row["ProductName"] = "Laptop";
        row["Price"] = 1199.99m;
        table.Rows.Add(row);

        row = table.NewRow();
        row["ProductName"] = "Smartphone";
        row["Price"] = 699.50m;
        table.Rows.Add(row);

        // Display data.
        foreach (DataRow r in table.Rows)
        {
            Console.WriteLine($"{r["ProductID"]}: {r["ProductName"]} - ${r["Price"]}");
        }

        // Save to XML.
        table.WriteXml("Products.xml");
    }
}