DateTime.TryParse还是Datetime.TryParseExact？

Question

I am converting date and time from a string. I append the date parts from my input like below

string joinedString = txtMonth.Text.Trim() + "/" + txtDate.Text.Trim() + "/" + txtYear.Text.Trim();

Generally i convert the string like below

DateTime dt;
if (DateTime.TryParse(joinedString, out dt))
{
    lblOutputCulture.Text = dt.ToString();
}
else
{
    lblOutputCulture.Text = "Invalid Date Time!!!";
}

Here i can get the datetime if the culture and datetime format of the culture is same as my string pattern. But if it is chnaged like 'dd-MM-yy' the conversion shoul failed.

To overcome this, we need to parse using InvariantCulture. For this i found 2 methods

Method 1 : Using DateTime.TryParse

if (DateTime.TryParse(joinedString, CultureInfo.InvariantCulture, DateTimeStyles.None, out dt))
{
    lblOutput.Text = dt.ToString();
}
else
{
    lblOutput.Text = "Invalid Date Time!!!";
}

Here the date time is successfully converted even if the datetime format of the system is changed. Also the following advatages i) The date and month input is 1 digit or 2 digit ii) The year input is 2 digit or 4 digit

Method 2: Using DateTime.TryParseExact

if (DateTime.TryParseExact(joinedString, "M/d/yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out dt))
{
    lblOutput.Text = dt.ToString();
}
else
{
    lblOutput.Text = "Invalid Date Time!!!";
}

Here also datetime is converted with out culture specific but strict to the format i gave in the tryparseexact statement.

But the following are the issues for this i) If i gave 4 digit year input it shows invalid date and time. If i change the format to 'M/d/yyyy' i can't able to give 2 digit year number. Like if i add time part, i need to give time part mandatory.

So which one is better? Please give a suggestion. But mostly i found the second method in all blogs and forums..

Which one is correct?

Answer 1

I would use neither:

try {
  DateTime dt = new DateTime(int.Parse(txtYear.Text),
                             int.Parse(txtMonth.Text),
                             int.Parse(txtDate.Text));
   lblOutput.Text = dt.ToString(); //Not sure why we'd do this, but whatever
} catch (ArgumentOutOfRangeException) {
   lblOutput.Text = "Invalid Date Time!!!";
}

This easily extends to including other parts, eg time, by selecting a different overload of the constructor .