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Checking the Text Box field is for numeric input only.

I created a form-based program that needs some input validation. I need to make sure that the user can only enter numeric values ​​within the text box.

So far, I have verified that the text field has something in it, but if it matters, then you need to continue checking that the entered value is numeric:

else if (txtEvDistance.Text.Length == 0)
        {
            MessageBox.Show("Please enter the distance");
        }
else if (cboAddEvent.Text //is numeric)
        {
            MessageBox.Show("Please enter a valid numeric distance");
        }
+8
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10 answers

You can try the TryParse method , which allows you to parse a string into an integer and return a boolean indicating the success or failure of the operation.

int distance;
if (int.TryParse(txtEvDistance.Text, out distance))
{
    // it a valid integer => you could use the distance variable here
}
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TextBox, Event OnKeyPress :

private void txtAditionalBatch_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsDigit(e.KeyChar)) e.Handled = true;         //Just Digits
            if (e.KeyChar == (char)8) e.Handled = false;            //Allow Backspace
            if (e.KeyChar == (char)13) btnSearch_Click(sender, e);  //Allow Enter            
        }

, TextBox ( /), .

+6

try
{
    int temp=Convert.ToInt32(txtEvDistance.Text);
}
catch(Exception h)
{
    MessageBox.Show("Please provide number only");
}
+5

javascript validator .

Javascript

script type="text/javascript" language="javascript">
    function validateNumbersOnly(e) {
        var unicode = e.charCode ? e.charCode : e.keyCode;
        if ((unicode == 8) || (unicode == 9) || (unicode > 47 && unicode < 58)) {
            return true;
        }
        else {

            window.alert("This field accepts only Numbers");
            return false;
        }
    }
</script>

( ValidationExpression)

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator ID="RegularExpressionValidator6" runat="server" Display="None" ErrorMessage="Accepts only numbers." ControlToValidate="TextBox1" ValidationExpression="^[0-9]*$" Text="*"></asp:RegularExpressionValidator>
+4

   // Check if the point entered is numeric or not
   if (Int32.TryParse(txtEvDistance.Text, out var outParse))
    {
       // Do what you want to do if numeric
    }
   else
    {
       // Do what you want to do if not numeric
    }
+2

Int.TryParse, Regex.

 Regex nonNumericRegex = new Regex(@"\D");
 if (nonNumericRegex.IsMatch(txtEvDistance.Text))
 {
   //Contains non numeric characters.
   return false;
 }
+2

, :

    public static bool IsNumeric(this object value)
    {
        if (value == null || value is DateTime)
        {
            return false;
        }

        if (value is Int16 || value is Int32 || value is Int64 || value is Decimal || value is Single || value is Double || value is Boolean)
        {
            return true;
        }

        try
        {
            if (value is string)
                Double.Parse(value as string);
            else
                Double.Parse(value.ToString());
            return true;
        }
        catch { }
        return false;
    }

. , .

+1
        if (int.TryParse(txtDepartmentNo.Text, out checkNumber) == false)
        {
            lblMessage.Text = string.Empty;
            lblMessage.Visible = true;
            lblMessage.ForeColor = Color.Maroon;
            lblMessage.Text = "You have not entered a number";
            return;
        }
+1

There is a solution here that allows either a numerical value with only a minus sign or a decimal sign with a minus sign and a decimal point. Most of the previous answers did not take into account the selected text. If you change the ShortcutsEnabled text box to false, you also cannot insert garbage into the text box (it disables right-clicking). Some solutions allowed you to enter data up to a minus. Please make sure I catch everything!

        private bool DecimalOnly_KeyPress(TextBox txt, bool numeric, KeyPressEventArgs e)
        {
            if (numeric)
            {
                // Test first character - either text is blank or the selection starts at first character.
                if (txt.Text == "" || txt.SelectionStart == 0)
                {
                    // If the first character is a minus or digit, AND
                    // if the text does not contain a minus OR the selected text DOES contain a minus.
                    if ((e.KeyChar == '-' || char.IsDigit(e.KeyChar)) && (!txt.Text.Contains("-") || txt.SelectedText.Contains("-")))
                        return false;
                    else
                        return true;
                }
                else
                {
                    // If it not the first character, then it must be a digit or backspace
                    if (char.IsDigit(e.KeyChar) || e.KeyChar == Convert.ToChar(Keys.Back))
                        return false;
                    else
                        return true;
                }
            }
            else
            {
                // Test first character - either text is blank or the selection starts at first character.
                if (txt.Text == "" || txt.SelectionStart == 0)
                {
                    // If the first character is a minus or digit, AND
                    // if the text does not contain a minus OR the selected text DOES contain a minus.
                    if ((e.KeyChar == '-' || char.IsDigit(e.KeyChar)) && (!txt.Text.Contains("-") || txt.SelectedText.Contains("-")))
                        return false;
                    else
                    {
                        // If the first character is a decimal point or digit, AND
                        // if the text does not contain a decimal point OR the selected text DOES contain a decimal point.
                        if ((e.KeyChar == '.' || char.IsDigit(e.KeyChar)) && (!txt.Text.Contains(".") || txt.SelectedText.Contains(".")))
                            return false;
                        else
                            return true;
                    }
                }
                else
                {
                    // If it not the first character, then it must be a digit or backspace OR
                    // a decimal point AND
                    // if the text does not contain a decimal point or the selected text does contain a decimal point.
                    if (char.IsDigit(e.KeyChar) || e.KeyChar == Convert.ToChar(Keys.Back) || (e.KeyChar == '.' && (!txt.Text.Contains(".") || txt.SelectedText.Contains("."))))
                        return false;
                    else
                        return true;
                }

            }
        }
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To check if a value is double:

private void button1_Click(object sender, EventArgs e)
{

    if (!double.TryParse(textBox1.Text, out var x))
    {
        System.Console.WriteLine("it not a double ");
        return;
    }
    System.Console.WriteLine("it a double ");
}
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