Validate date textbox

Question

I'm using the following code to check if a valid date has been typed into a textbox:

public bool ValidateDate(Control ctrl)
{
    if (!string.IsNullOrEmpty(ctrl.Text))
    {
        DateTime value;
        if (!DateTime.TryParse(ctrl.Text, out value))
        {
            return false;
        }
    }
    return true;
}


private void txtStartDate_Validating(object sender, CancelEventArgs e)
{
    if (Utils.ValidateDate(txtStartDate))
    {
        errorProvider.SetError(txtStartDate, "");
    }
    else
    {
        errorProvider.SetError(txtStartDate, "* Invalid Date");
        e.Cancel = true;
    }
}

This works fine for dates that are entered m/d/yy, m/d/yyyy, mm/dd/yy, mm/dd/yyyy. If a user enters in a date such as "11/17" this will evaluate to a valid date, but, unfortunately, I only want dates that have all three date parts.

Is there an easy way to do this? I was thinking something a long the lines of checking if there are 2 "/" in the textbox, but I'm sure there is a cleaner way of achieving the desired result.

EDIT: Thanks for all the suggestions everyone! I ended up using the following code which accepts M/d/yyyy and M/d/yy ~

    public bool ValidateDate(Control ctrl)
    {          
        if (!string.IsNullOrEmpty(ctrl.Text))
        {
            string[] formats = {"M/d/yyyy", "M/d/yy"};
            DateTime value;

            if  (!DateTime.TryParseExact(ctrl.Text, formats, new CultureInfo("en-US"), DateTimeStyles.None, out value))
            {
                return false;
            }                
        }
        return true;
    }

Solution 1

The DateTime.TryParseExact(..) function does allow you to parse a date using a specific date format (for example, "mm/dd/yyyy"). However, if you want to be flexible on the number of digits in the year, then a regex might be a better choice.

Solution 2

You could try using regular expressions:

Regex dateRegExp = new Regex("^(((0?[1-9]|[12]\d|3[01])[\.\-\/](0?[13578]|1[02])[\.\-\/]((1[6-9]|[2-9]\d)?\d{2}|\d))|((0?[1-9]|[12]\d|30)[\.\-\/](0?[13456789]|1[012])[\.\-\/]((1[6-9]|[2-9]\d)?\d{2}|\d))|((0?[1-9]|1\d|2[0-8])[\.\-\/]0?2[\.\-\/]((1[6-9]|[2-9]\d)?\d{2}|\d))|(29[\.\-\/]0?2[\.\-\/]((1[6-9]|[2-9]\d)?(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)|00|[048])))$");

Match m = dateRegExp.Match(dateString);

if (m.Success) {
    //Valid Date'
}
else
{

    //No soup for you, 1 year'
}

(I "borrowed" the regexp from here: RegExpLib)

Comments

[t0mm13b]

Don't forget, if you want to be flexible, whether to account for regional settings for DateTime, it could be dd/mm/yyyy (UK), mm/dd/yyyy (USA), or even yyyy/mm/dd, the slash separator could be different as well. Use the cultureinfo class to handle this..

[Wil P]

Nice. I totally forgot about TryParseExact. +1 from me.

[Sesame]

Normally, I would have... but, I am using Telerik's WinForms controls and I've just had too many problems with their MaskedEditBox. Thanks for the suggestion, any way.

[Sesame]

The DateTime.TryParseExact() has an override to accept multiple formats so I didn't have to give up the formatting flexibility. Thanks!

[Neil]

Excellent. I had forgotten about that overload. I'm glad that worked for you.