How to Validate a DateTime in C#?

I doubt I am the only one who has come up with this solution, but if you have a better one please post it here. I simply want to leave this question here so I and others can search it later.

I needed to tell whether a valid date had been entered into a text box and this is the code that I came up with. I fire this when focus leaves the text box.

try
{
    DateTime.Parse(startDateTextBox.Text);
}
catch
{
    startDateTextBox.Text = DateTime.Today.ToShortDateString();
}

DateTime.TryParse

This I believe is faster and it means you dont have to use ugly try/catches :)

e.g

DateTime temp;
if(DateTime.TryParse(startDateTextBox.Text, out temp))
{
  // Yay :)
}
else
{
  // Aww.. :(
}

Don't use exceptions for flow control. Use DateTime.TryParse and DateTime.TryParseExact. Personally I prefer TryParseExact with a specific format, but I guess there are times when TryParse is better. Example use based on your original code:

DateTime value;
if (!DateTime.TryParse(startDateTextBox.Text, out value))
{
    startDateTextox.Text = DateTime.Today.ToShortDateString();
}

Reasons for preferring this approach:

• Clearer code (it says what it wants to do)
• Better performance than catching and swallowing exceptions
• This doesn't catch exceptions inappropriately - e.g. OutOfMemoryException, ThreadInterruptedException. (Your current code could be fixed to avoid this by just catching the relevant exception, but using TryParse would still be better.)

Here's another variation of the solution that returns true if the string can be converted to a DateTime type, and false otherwise.

public static bool IsDateTime(string txtDate)
{
	DateTime tempDate;
	return DateTime.TryParse(txtDate, out tempDate);
}

All the Answers are Quite great but if you want to use a single function ,this may work. It will work with other date format but wont work with this date eg:05/06/202 it will consider it as valid date but it isnt.

private bool validateTime(string dateInString)
{
    DateTime temp;
    if (DateTime.TryParse(dateInString, out temp))
    {
       return true;
    }
    return false;
}

I would use the DateTime.TryParse() method: http://msdn.microsoft.com/en-us/library/system.datetime.tryparse.aspx

What about using TryParse?

A problem with using DateTime.TryParse is that it doesn't support the very common data-entry use case of dates entered without separators, e.g. 011508.

Here's an example of how to support this. (This is from a framework I'm building, so its signature is a little weird, but the core logic should be usable):

    private static readonly Regex ShortDate = new Regex(@"^\d{6}$");
    private static readonly Regex LongDate = new Regex(@"^\d{8}$");

    public object Parse(object value, out string message)
    {
        msg = null;
        string s = value.ToString().Trim();
        if (s.Trim() == "")
        {
            return null;
        }
        else
        {
            if (ShortDate.Match(s).Success)
            {
                s = s.Substring(0, 2) + "/" + s.Substring(2, 2) + "/" + s.Substring(4, 2);
            }
            if (LongDate.Match(s).Success)
            {
                s = s.Substring(0, 2) + "/" + s.Substring(2, 2) + "/" + s.Substring(4, 4);
            }
            DateTime d = DateTime.MinValue;
            if (DateTime.TryParse(s, out d))
            {
                return d;
            }
            else
            {
                message = String.Format("\"{0}\" is not a valid date.", s);
                return null;
            }
        }

    }

One liner:

if (DateTime.TryParse(value, out _)) {//dostuff}

    protected bool ValidateBirthday(String date)
    {
        DateTime Temp;

        if (DateTime.TryParse(date, out Temp) == true &&
      Temp.Hour == 0 &&
      Temp.Minute == 0 &&
      Temp.Second == 0 &&
      Temp.Millisecond == 0 &&
      Temp > DateTime.MinValue)
            return true;
        else
            return false;
    }

//suppose that input string is short date format.
e.g. "2013/7/5" returns true or
"2013/2/31" returns false.
http://forums.asp.net/t/1250332.aspx/1
//bool booleanValue = ValidateBirthday("12:55"); returns false

private void btnEnter_Click(object sender, EventArgs e)
{
    maskedTextBox1.Mask = "00/00/0000";
    maskedTextBox1.ValidatingType = typeof(System.DateTime);
    //if (!IsValidDOB(maskedTextBox1.Text)) 
    if (!ValidateBirthday(maskedTextBox1.Text))
        MessageBox.Show(" Not Valid");
    else
        MessageBox.Show("Valid");
}
// check date format dd/mm/yyyy. but not if year < 1 or > 2013.
public static bool IsValidDOB(string dob)
{ 
    DateTime temp;
    if (DateTime.TryParse(dob, out temp))
        return (true);
    else 
        return (false);
}
// checks date format dd/mm/yyyy and year > 1900!.
protected bool ValidateBirthday(String date)
{
    DateTime Temp;
    if (DateTime.TryParse(date, out Temp) == true &&
        Temp.Year > 1900 &&
       // Temp.Hour == 0 && Temp.Minute == 0 &&
        //Temp.Second == 0 && Temp.Millisecond == 0 &&
        Temp > DateTime.MinValue)
        return (true);
    else
        return (false);
}

You can also define the DateTime format for a specific CultureInfo

public static bool IsDateTime(string tempDate)
{
    DateTime fromDateValue;
    var formats = new[] { "MM/dd/yyyy", "dd/MM/yyyy h:mm:ss", "MM/dd/yyyy hh:mm tt", "yyyy'-'MM'-'dd'T'HH':'mm':'ss" };
    return DateTime.TryParseExact(tempDate, formats, System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out fromDateValue);
}

public static bool ValidateTime(string dateString)
{
    return DateTime.TryParse(dateString, out _);
}

DateTime temp;
try
{
	temp = Convert.ToDateTime(grd.Rows[e.RowIndex].Cells["dateg"].Value);
	grd.Rows[e.RowIndex].Cells["dateg"].Value = temp.ToString("yyyy/MM/dd");
}
catch 
{	
	MessageBox.Show("Sorry The date not valid", "Error", MessageBoxButtons.OK, MessageBoxIcon.Stop,MessageBoxDefaultButton.Button1,MessageBoxOptions .RightAlign);
	grd.Rows[e.RowIndex].Cells["dateg"].Value = null;
}

DateTime temp;
try
{
    temp = Convert.ToDateTime(date);
    date = temp.ToString("yyyy/MM/dd");
}
catch 
{
    MessageBox.Show("Sorry The date not valid", "Error", MessageBoxButtons.OK, MessageBoxIcon.Stop,MessageBoxDefaultButton.Button1,MessageBoxOptions .RightAlign);
    date = null;
}

protected static bool CheckDate(DateTime date)
{
	if(new DateTime() == date)		
		return false;		
	else		
		return true;		
}