Convert `List`, `DataTable`

The DataGridView control can display a List. This can be done by converting the List to a DataTable first.

Some notes

With some custom List-to-DataTable conversion logic, we get the best performance from the DataGridView by using the DataSource property.

An example

This example shows a List of string arrays. This is a data structure that could be parsed from a text file easily, as with the Split method.

Start We introduce the ConvertListToDataTable method, which converts a List to a DataTable.

Here We create a new empty DataTable. Next, we find the maximum number of columns that will be required by looping through the input List.

Then We add those columns, and then add all the rows. We return the DataTable.

using System;
using System.Collections.Generic;
using System.Data;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Example list.
            List<string[]> list = new List<string[]>();
            list.Add(new string[] { "Column 1", "Column 2", "Column 3" });
            list.Add(new string[] { "Row 2", "Row 2" });
            list.Add(new string[] { "Row 3" });

            // Convert to DataTable.
            DataTable table = ConvertListToDataTable(list);
            dataGridView1.DataSource = table;
        }

        static DataTable ConvertListToDataTable(List<string[]> list)
        {
            // New table.
            DataTable table = new DataTable();

            // Get max columns.
            int columns = 0;
            foreach (var array in list)
            {
                if (array.Length > columns)
                {
                    columns = array.Length;
                }
            }

            // Add columns.
            for (int i = 0; i < columns; i++)
            {
                table.Columns.Add();
            }

            // Add rows.
            foreach (var array in list)
            {
                table.Rows.Add(array);
            }

            return table;
        }
    }
}

Assign to `DataSource`

Once we have a DataTable instance, it is appropriate to assign it to the DataSource property. Assigning the List to the DataSource will not work correctly.

Note The DataSource provides the best performance for displaying large amounts of data instantly in a DataGridView.

Warning If you were to add Columns and Rows individually, slowdowns are more likely to occur.

Discussion

DataTable can be used as an optimization. Using controls in Windows Forms or WPF directly often results in rendering.

However This is often much slower, and more processor-intensive, than in-memory operations.

So When using DataGridView or similar controls, processing the data first seems like it might be slower, but it ends up much faster.

Summary

We converted a List of string arrays into a DataTable. This yielded a collection that can be displayed in a DataGridView with the DataSource property. Our code was effective.