DataTable RowChanged

DataTable provides many methods, properties and event handlers. The RowChanged event handler helps us detect when something changes in a DataTable.

Some notes

Sometimes there is an action that you need to take when a row changes in the DataTable. The RowChanged event handler may be helpful here.

This program creates a DataTable with 4 columns and 5 rows. It then hooks up the RowChanged event handler. To add RowChanged, type table.RowChanged and then the += characters.

using System;
using System.Data;

class Program
{
    static void Main()
    {
        DataTable table = new DataTable();

        // ... Unique id.
        table.Columns.Add("Id", typeof(int));
        table.Columns["Id"].Unique = true;

        table.Columns.Add("Dosage", typeof(int));
        table.Columns.Add("Drug", typeof(string));
        table.Columns.Add("Patient", typeof(string));

        // ... Five DataRows.
        table.Rows.Add(1, 25, "Evista", "Lundberg");
        table.Rows.Add(2, 50, "Adcirca", "Jeffries");
        table.Rows.Add(3, 10, "Glucagon", "Johnson");
        table.Rows.Add(4, 20, "Amyvid", "Skinner");
        table.Rows.Add(5, 80, "Alimta", "Nguyen");
        table.AcceptChanges();

        // ... Handle RowChanged.
        table.RowChanged += table_RowChanged;

        // ... Change a row.
        table.Rows[0]["Dosage"] = 50;
        table.Rows[0]["Dosage"] = -1;

        // ... Pause.
        Console.WriteLine("[Press enter]");
        Console.ReadLine();

        table.Rows[0]["Dosage"] = 15;
        table.Rows[1]["Dosage"] = 800;
    }

    static void table_RowChanged(object sender, DataRowChangeEventArgs e)
    {
        Console.WriteLine("... Changed:  " + (int)e.Row["Dosage"]);
    }
}
... Changed:  50
... Changed:  -1
[Press enter]

... Changed:  15
... Changed:  800

StackOverflowException

If you try to change a cell in the RowChanged event handler, an infinite loop may be entered. Each change will trigger another call to RowChanged.

A discussion

We can use RejectChanges and AcceptChanges to process changes to the DataTable contents. The RowChanged and RowChanging events may be helpful.

Summary

Code that handles DataTables tends to be complex and application-specific. Events like RowChanged, and methods like AcceptChanges are help in monitoring mutations.