TextBox Validation - C#

Question

Hello everyone,

I am having quite a hard time with my C# Application's textbox validation. The thing is, the said textbox should only accept decimal values. so it means, there should be no letters or any other symbols aside from the '.' symbol. The letter filter, i can handle. However, i don't exactly know how I can manage to filter the number of '.' that the textbox should accept. If anybody has any idea how to do this, please give me an idea.

Thank you very much :)

Answer 1

Just a thought: if you are monitoring the decimal places, simply keep a bool flag in your control to say "I've already had a dot"; subsequent dots are invalid.

Alternatively, when checking for decimal places, you can use Contains:

if (textbox.Text.Contains("."))

Also, review this sample available on MSDN (NumericTextBox):

http://msdn.microsoft.com/en-us/library/ms229644(VS.80).aspx

Answer 2

this should work!!!

modified for just one decimal

    private void txtType_KeyPress(object sender, KeyPressEventArgs e)
    {
        if (e.KeyChar == (char)Keys.Back || (e.KeyChar == (char)'.') && !(sender as TextBox).Text.Contains("."))
        {
            return;
        }
        decimal isNumber = 0;
        e.Handled = !decimal.TryParse(e.KeyChar.ToString(), out isNumber);
    }

Answer 3

Use regex validation:

^([0-9]*|\d*\.\d{1}?\d*)$

This site has a library of regex validation (including numeric related) that you'll find useful:

http://regexlib.com/Search.aspx?k=decimal&c=-1&m=-1&ps=20

Answer 4

decimal value;
bool isValid = decimal.TryParse(textBox.Text, out value);

if (!isValid)
{
    throw new ArgumentException("Input must be a decimal value");
}

Answer 5

Use a MaskedTextBox instead and set the mask to only accept decimals.