Custom TextBox that accepts Decimal in C#.NET

Question

I've created a custom TextBox for Windows Application using C#.NET. It must accept decimal (floated point numbers) like 8.32 and 16.002.

I've constructed the following algorithm. It is accepting pure numbers only. I can't figure out how to make it accept float as well.

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

namespace SmartTextBoxLib
{
    public partial class SmartTextBox : TextBox
    {
        public SmartTextBox()
        {
            InitializeComponent();
        }
        protected override void OnKeyPress(KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar))
            {
                e.Handled = true;
            }
            base.OnKeyPress(e);
        }
    }
}

OnKeyPress is the wrong event to use. What if someone would paste text in your text box with the mouse? You should simply use one of the existing masked text-boxes out there. — Daniel Hilgarth
– Daniel Hilgarth, Commented Oct 12, 2012 at 11:14
I'm aware of the existance of Masked Text-Boxes. I'm simply trying to reinvent the wheel for the sake of learning. So if you can suggest any alternative solution, it will be appreciated. — Samik Sengupta
– Samik Sengupta, Commented Oct 12, 2012 at 11:20

Şafak Gür · Accepted Answer · 2012-10-12 11:35:07Z

1

You can use:

if (!char.IsDigit(e.KeyChar) && e.KeyChar != '.')
    e.Handled = true;
base.OnKeyPress(e);

That allows digit characters or .. You can make it , if you use that to seperate decimals.

Or, you could do this:

decimal value;
e.Handled = !decimal.TryParse((sender as TextBox).Text + e.KeyChar, out value);
base.OnKeyPress(e);

edited Oct 12, 2012 at 11:35

answered Oct 12, 2012 at 11:29

Şafak Gür

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6 Comments

Kevin Gosse Over a year ago

So 21.47..1.5.. is a valid number?

Samik Sengupta Over a year ago

Thanks. With a little more modification like OnTextChanged event modifications I can finally make it work and define numbers like 21.47..1.5.. as invalid.

Şafak Gür Over a year ago

@Samik: Added an alternative.

Samik Sengupta Over a year ago

Thanks so much. It's a better alternative to the one I was planning.

Şafak Gür Over a year ago

@Samik: Oops, I just realized that I need to add + e.KeyChar part and edited the answer.

|

Justin Harvey · Accepted Answer · 2012-10-12 11:15:22Z

1

Use the

System.Windows.Forms.NumericUpDown

instead, it will do this for you.

answered Oct 12, 2012 at 11:15

Justin Harvey

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3 Comments

Samik Sengupta Over a year ago

And call what event? Or check what condition?

Şafak Gür Over a year ago

@Samik: It has a Decimal property called Value.

Samik Sengupta Over a year ago

I see. But If I wanted to modify a TextBox's behaviour into accepting decimal only, how should I rewrite my algorithm?

giacomelli · Accepted Answer · 2012-10-12 11:31:24Z

0

You can use MaskedTextBox instead Texbox control.

Defined the Mask property on MaskedTextBox control:

maskedTextBoxInstance.Mask = "99.000";

answered Oct 12, 2012 at 11:31

giacomelli

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