Use enter key for submission

Question

I have created a customtextbox which on pressing enter moves to next control (in tab order) . Now i have used many textboxes on a single form (form which acts as a data entry form ) . Now i am looking for a way in which when the user reaches last of these custom textboxes , fills the data in it ( last textbox ) and presses enter , I can submit the all textboxes data to my database .

 public partial class customtextbox : TextBox
    {
        
        public customtextbox()
        {          
             InitializeComponent();
        }
        protected override void OnEnter(EventArgs e)
        {
            base.OnEnter(e);
           
        }

        protected override void OnLeave(EventArgs e)
        {
            base.OnLeave(e);
         
        }
        protected override void OnKeyDown(KeyEventArgs e)
        {
            base.OnKeyDown(e);

                if (e.KeyCode == Keys.Enter || e.KeyCode == Keys.Down)
                {
                    SendKeys.Send("{TAB}");

                    //disable beep 
                    e.Handled = e.SuppressKeyPress = true;
                }
                if ((e.KeyCode == Keys.Back || e.KeyCode == Keys.Up) && this.Text.Length == 0)
                {
                    SendKeys.Send("+{TAB}");
                }
            
        }
}

I don't want any button or hidden button on my Form . Another problem is if I used the form keydown event to capture enter key and set the keypreview property to true and do my desired thing , the above code from the customtextbox

SendKeys.Send("{TAB}");

doesn't work as the form's keydown event eats it up . Please suggest me a way to get this when the focus is inside the last customtextbox .

Answer 1

Here is a quick-n-dirty sample missing moving backwards.

using System.ComponentModel;
using System.Diagnostics;

#pragma warning disable CS8618

namespace WinFormsApp1;

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

    private void Form1_Load(object sender, EventArgs e)
    {
        Controls
            .OfType<NoBeepTextBox>()
            .ToList()
            .ForEach(b => { b.TriggerEvent += OnTriggerEvent; });
    }

    private void OnTriggerEvent(bool last, string name)
    {
        if (last)
        {
            Debug.WriteLine($"Button {name} call to database save method");
        }
    }
}

/// <summary>
/// Place in a class file
/// </summary>
public class NoBeepTextBox : TextBox
{
    /// <summary>
    /// We really do not need name, here just to show you the correct
    /// TextBox was used
    /// </summary>
    public delegate void TriggerDelegate(bool isLast, string name);
    public event TriggerDelegate TriggerEvent;
    protected override void OnKeyDown(KeyEventArgs e)
    {
        if (e.KeyCode == (Keys.Return))
        {
            e.Handled = true;
            e.SuppressKeyPress = true;

            TriggerEvent?.Invoke(Last, Name);

            if (!Last)
            {
                SendKeys.Send("{TAB}");
            }
            
            return;
        }

        base.OnKeyDown(e);
    }

    /// <summary>
    /// Set the last TextBox to true in the form designer
    /// </summary>
    [Category("Behavior"), Description("Last TextBox")]
    public bool Last { get; set; }
}