C# windows forms - How can I only allow integers to be input into textboxes?

Question

I am fairly new to C#, and this is my first attempt at creating a windows form. I created a very simple calculator which has two textboxes for users to enter numbers into. It has a(n) Add, Subtract, Multiply, and Divide button, and when the user enters values into the textboxes and clicks one of the buttons, the result is shown in a label. I would like to only allow integers to be input into the textboxes, but I don't know how I would be able to do this. Any advice or recommendations are appreciated. Thanks.

Here is my code so far:

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

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void AddBtn_Click(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text))
            ResultLbl.Text = (Convert.ToInt32(textBox1.Text) + Convert.ToInt32(textBox2.Text)).ToString();
    }

    private void SubtractBtn_Click(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text))
            ResultLbl.Text = (Convert.ToInt32(textBox1.Text) - Convert.ToInt32(textBox2.Text)).ToString();
    }

    private void MultiplyBtn_Click(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text))
            ResultLbl.Text = (Convert.ToInt32(textBox1.Text) * Convert.ToInt32(textBox2.Text)).ToString();
    }

    private void DivideBtn_Click(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text))
            ResultLbl.Text = (Convert.ToInt32(textBox1.Text) / Convert.ToInt32(textBox2.Text)).ToString();
    }
}

}

If it is a calculator, NumericUpDowns might be more appropriate. They still wont be integers but wont allow letters. Please read [ask] and take the [tour] — Ňɏssa Pøngjǣrdenlarp, Sep 15 '17 at 00:14

Prashanth kumar · Accepted Answer · 2017-09-16T01:53:28.800

2

You can use the below Function, and add it for Key press event of the text box.

private void txtbox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar))
            {
                e.Handled = true;
            }
        }

edited Sep 16 '17 at 01:53

answered Sep 15 '17 at 00:26

Prashanth kumar

949
3
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32

score 0 · Answer 2 · answered Sep 15 '17 at 00:35

0

Simplest way is to use the NumericUpDown control instead TextBox. NumericUpDown only allows numbers as their input and have similar properties of TextBox.

Access the value like this :

decimal answer=numericUpDown1.Value

`

answered Sep 15 '17 at 00:35

Beingnin

2,288
1
21
37

score 0 · Answer 3 · answered Sep 15 '17 at 00:37

0

Use NumericUpDown

You can find here a similar question How do I make a textbox that only accepts numbers?

answered Sep 15 '17 at 00:37

Mhd

2,778
5
22
59

score -1 · Answer 4 · answered Sep 15 '17 at 01:45

-1

make it simple try this

//function
public static void NumberOnly(object sender, KeyPressEventArgs e)
{
     e.Handled = !char.IsDigit(e.KeyChar) && !char.IsControl(e.KeyChar);
}

//to call used this
NumberOnly("your textbox");

answered Sep 15 '17 at 01:45

Ramgy Borja

2,330
2
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40

C# windows forms - How can I only allow integers to be input into textboxes?

4 Answers4