C# Numeric Only TextBox Control [duplicate]

Question

This question already has an answer here:

• numeric-only textbox as a control in Visual Studio toolbox 4 answers

I am using C#.NET 3.5, and I have a problem in my project. In C# Windows Application, I want to make a textbox to accept only numbers. If user try to enter characters message should be appear like "please enter numbers only", and in another textbox it has to accept valid email id message should appear when it is invalid. It has to show invalid user id.

Answer 1

use this code:

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            const char Delete = (char)8;
            e.Handled = !Char.IsDigit(e.KeyChar) && e.KeyChar != Delete;
        }

Answer 2

I used the TryParse that @fjdumont mentioned but in the validating event instead.

private void Number_Validating(object sender, CancelEventArgs e) {
    int val;
    TextBox tb = sender as TextBox;
    if (!int.TryParse(tb.Text, out val)) {
        MessageBox.Show(tb.Tag +  " must be numeric.");
        tb.Undo();
        e.Cancel = true;
    }
}

I attached this to two different text boxes with in my form initializing code.

    public Form1() {
        InitializeComponent();
        textBox1.Validating+=new CancelEventHandler(Number_Validating);
        textBox2.Validating+=new CancelEventHandler(Number_Validating);
    }

I also added the tb.Undo() to back out invalid changes.

Answer 3

You can check the Ascii value by e.keychar on KeyPress event of TextBox.

By checking the AscII value you can check for number or character.

Similarly you can write logic to check the Email ID.

Answer 4

You might want to try int.TryParse(string, out int) in the KeyPress(object, KeyPressEventArgs) event to check for numeric values. For the other problem you could use regular expressions instead.