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Cannot implicitly convert type bool to System.DateTime (C#)

I'm trying to convert a string to datetime to validate if user input is actually a date.
The error I'm getting is:
Cannot implicitly convert type bool to System.DateTime.
I've been looking online for a while and can't find anything specific enough to help me understand.
Code:
public bool is21YearsOfAge(string argument)
{
DateTime _parsedDateArgument;
DateTime convertStringToDate = System.DateTime.TryParse(argument, out >_parsedDateArgument);
if (convertStringToDate > DateTime.Now)
{
//do something
}
}
Thanks in advance.

The TryParse method returns a bool that informs you whether the parse was successful, rather than throwing an exception like the Parse method does. Try doing this:
DateTime convertStringToDate;
bool isDate = DateTime.TryParse(argument, out convertStringToDate);
If argument is a date, convertStringToDate will contain that date as a DateTime.

DateTime.TryParse returns bool to indicate if parsing was successeful. So you should do
System.DateTime.TryParse(argument, out _parsedDateArgument);
DateTime convertStringToDate =_parsedDateArgument

Look at the documentation for DateTime.TryParse - it returns a bool, but has an out parameter for the parsed result:
DateTime dateTime;
bool success = DateTime.TryParse(text, out dateTime);
If success is false, that means the text couldn't be parsed. (So typically at this point you'd display an error to the user.)
You've already got the out parameter - why did you expect to end up with two different DateTime values (one as the return value and one from the out parameter)?
When you get an error like this, always read the documentation as the first step towards diagnosing the problem.

It should be
DateTime convertStringToDate;
if(System.DateTime.TryParse(argument, out convertStringToDate))
{
//Now you will have converted date in convertStringToDate
if (convertStringToDate > DateTime.Now)
{
//do something
}
}
else
{
//argument not have a valid date
}
System.DateTime.TryParse will retrun true if, argument will have a valid date string to convert. and the converted date will be store in its out parameter.

DateTime.TryParse do not return a DateTime value. It returns a bool indicating if it could parse it.
Instead use
DateTime convertStringToDate;
if(DateTime.TryParse(argument, out convertStringToDate)){
//ok value is good
}else{
//Not ok value is not good
}

use this instead,
DateTime _parsedDateArgument;
bool success = System.DateTime.TryParse(argument, out _parsedDateArgument);
Always remember that Tryparse always return boolean.

TryParse returns a bool, use just Parse instead, or assign the out variable to the new you have:
System.DateTime.TryParse(argument, out _parsedDateArgument);
DateTime convertStringToDate = _parsedDateArgument;
or like this:
DateTime convertStringToDate = DateTime.Parse(argument);

add the following namespace
using System.Globalization;
Create object of CultureInfo class
CultureInfo MyCI = new CultureInfo("en-US");
DateTime convertStringToDate = System.DateTime.TryParse(argument.ToString("MM/dd/yy", MyCI), out _parsedDateArgument);

How to validate DateTime format?

I am suppose to let the user enter a DateTime format, but I need to validate it to check if it is acceptable. The user might enter "yyyy-MM-dd" and it would be fine, but they can also enter "MM/yyyyMM/ddd" or any other combination. Is there a way to validate this?

Are you looking for something like this?
DateTime expectedDate;
if (!DateTime.TryParse("07/27/2012", out expectedDate))
{
Console.Write("Luke I am not your datetime.... NOOO!!!!!!!!!!!!!!");
}
If your user knows the exact format(s) needed...
string[] formats = { "MM/dd/yyyy", "M/d/yyyy", "M/dd/yyyy", "MM/d/yyyy" };
DateTime expectedDate;
if (!DateTime.TryParseExact("07/27/2012", formats, new CultureInfo("en-US"),
DateTimeStyles.None, out expectedDate))
{
Console.Write("Thank you Mario, but the DateTime is in another format.");
}

I don't know of any way to actually validate the format they enter since sometimes you want to intentionally include characters that translate into anything. One thing you might consider is allowing the user to self validate by showing a preview of what their entered format translates into.

I assume you want to know if the specified format string is valid...
For this you could round-trip it:
private bool IsValidDateFormat(string dateFormat)
{
try
{
String dts=DateTime.Now.ToString(dateFormat, CultureInfo.InvariantCulture);
DateTime.ParseExact(dts, dateFormat, CultureInfo.InvariantCulture);
return true;
}
catch (Exception)
{
return false;
}
}

Unless I am remembering incorrectly, the only invalid DateTime format strings are one character long. You can assume any 2 or more character DateTime format string is valid.
DateTime.ParseExact("qq", "qq", null) == DateTime.Today
DateTime.ParseExact("myy", "501", null) == "05/01/2001"
Standard (1 character)
Custom (>1 character)
For reference, allowed single character strings as formats:
d,D,f,F,g,G,m,M,o,O,r,R,s,T,u,U,y,Y
Any other character, such as q, by itself is invalid. All other strings will be successfully parsed as formatting strings.

You don't talk about your validation strategy. Anyway you should use something involving regular expressions and than apply allowed patterns. This would help against the formal validity .. then you have to take care about the actual contents and be sure the values are correct according as month, day and year.
Anyway several people suggested to use the DateTime.TryParse() method to let the substrate take care for you. But you'll have to specify the format anyway! so there's no magic! you would fall in ambiguity otherwise

This works for me-
try
{
String formattedDate = DateTime.Now.ToString(dateFormat);
DateTime.Parse(formattedDate);
return true;
}
catch (Exception)
{
return false;
}

static private bool IsValidDateFormat(string dateFormat)
{
try
{
DateTime pastDate = DateTime.Now.Date.Subtract(new TimeSpan(10, 0, 0, 0, 0));
string pastDateString = pastDate.ToString(dateFormat, CultureInfo.InvariantCulture);
DateTime parsedDate = DateTime.ParseExact(pastDateString, dateFormat, CultureInfo.InvariantCulture);
if (parsedDate.Date.CompareTo(pastDate.Date) ==0)
{
return true;
}
return false;
}
catch
{
return false;
}
}
I do use this code - it is a modification of shapiro yaacov posting.
It looks as "DateTime.ParseExact" does not throw an exception when using an invalid dateformat string - it just returns "DateTime.Now".
My approach is to convert a date in the past to string and then check if this is returned by ParseExact()

The answer by ZipXap accepts any format that doesn't throw an exception, yet something like "aaaa" will pass that validation and give the current date at midnight ("26-Apr-22 00:00:00" when writing this).
A better aproach is to use the DateTimeStyles.NoCurrentDateDefault option and compare the result to default:
using System.Globalization;
var format = "aaaaa";
try {
var dt = DateTime.ParseExact(
DateTime.Now.ToString(format, CultureInfo.InvariantCulture),
format,
CultureInfo.InvariantCulture,
DateTimeStyles.NoCurrentDateDefault);
return dt != default;
} catch {
return false;
}
/*
"aaaaa" -> false
"h" -> false
"hh" -> true
"fff" -> true
"gg" -> false
"yyyy gg" -> true
"'timezone: 'K" -> false
"zzz" -> false
*/

My solution was to mark the input-field as read-only and allow users to change the value only by jqueryui datepicker.
It is intuitive. You can specify your preferred format and need only to validate this one format.
Otherwise you may get really in trouble. What are you going to do with "02/03/2020" in USA you interpret it as the third of February, but for south america it is definitely the second of March. And there are a lot of other Date formats around the globe.

Valid date check with DateTime.TryParse method

I am using Datetime.TryParse method to check the valid datetime. the input date string would be any string data. but is returning false as the specify date in invalid.
DateTime fromDateValue;
if (DateTime.TryParse("15/07/2012", out fromDateValue))
{
//do for valid date
}
else
{
//do for in-valid date
}
Edit: I missed. I need to check the valid date with time as "15/07/2012 12:00:00".
Any suggestions are welcome.

You could use the TryParseExact method which allows you to pass a collection of possible formats that you want to support. The TryParse method is culture dependent so be very careful if you decide to use it.
So for example:
DateTime fromDateValue;
string s = "15/07/2012";
var formats = new[] { "dd/MM/yyyy", "yyyy-MM-dd" };
if (DateTime.TryParseExact(s, formats, CultureInfo.InvariantCulture, DateTimeStyles.None, out fromDateValue))
{
// do for valid date
}
else
{
// do for invalid date
}

You should be using TryParseExact as you seem to have the format fixed in your case.
Something like can also work for you
DateTime.ParseExact([yourdatehere],
new[] { "dd/MM/yyyy", "dd/M/yyyy" },
CultureInfo.InvariantCulture,
DateTimeStyles.None);

As the others said, you can use TryParseExact.
For more informations and the use with the time, you can check the MSDN Documentation

How do I convert a 12 hour time string into a C# TimeSpan?

When a user fills out a form, they use a dropdown to denote what time they would like to schedule the test for. This drop down contains of all times of the day in 15 minute increments in the 12 hour AM/PM form. So for example, if the user selects 4:15 pm, the server sends the string "4:15 PM" to the webserver with the form submittion.
I need to some how convert this string into a Timespan, so I can store it in my database's time field (with linq to sql).
Anyone know of a good way to convert an AM/PM time string into a timespan?

You probably want to use a DateTime instead of TimeSpan. You can use DateTime.ParseExact to parse the string into a DateTime object.
string s = "4:15 PM";
DateTime t = DateTime.ParseExact(s, "h:mm tt", CultureInfo.InvariantCulture);
//if you really need a TimeSpan this will get the time elapsed since midnight:
TimeSpan ts = t.TimeOfDay;

Easiest way is like this:
var time = "4:15 PM".ToTimeSpan();
.
This takes Phil's code and puts it in a helper method. It's trivial but it makes it a one line call:
public static class TimeSpanHelper
{
public static TimeSpan ToTimeSpan(this string timeString)
{
var dt = DateTime.ParseExact(timeString, "h:mm tt", System.Globalization.CultureInfo.InvariantCulture);
return dt.TimeOfDay;
}
}

Try this:
DateTime time;
if(DateTime.TryParse("4:15PM", out time)) {
// time.TimeOfDay will get the time
} else {
// invalid time
}

I like Lee's answer the best, but acermate would be correct if you want to use tryparse. To combine that and get timespan do:
public TimeSpan GetTimeFromString(string timeString)
{
DateTime dateWithTime = DateTime.MinValue;
DateTime.TryParse(timeString, out dateWithTime);
return dateWithTime.TimeOfDay;
}

Try:
string fromServer = <GETFROMSERVER>();
var time = DateTime.Parse(fromServer);
That gets you the time, if you create the end time as well you can get Timespans by doing arithmetic w/ DateTime objects.

How to compare a DateTime to a string

I have string which contains a time (obtained from a DB):
string user_time = "17:10:03"; //Hours:minutes:seconds
DateTime time_now = DateTime.Now;
How do I compare this string to a DateTime? I'd like something like this:
if(time_now > user_time)
{
//Do something
}
else
{
//Do something
}

DateTime supports comparison, but first you need to parse the date-time string, DateTime.Parse() should suffice:
var dateTimeStr = "17:10:03";
var user_time = DateTime.Parse( dateTimeStr );
var time_now = DateTime.Now;
if( time_now > user_time )
{
// your code...
}
Bear in mind, that comparing dates/times sometimes requires awareness of time-zones to make the comparison meaningful.

The problem is that DateTime.Now includes a date, "17:10:03" doesn't. Do it like this:
Dim dbaseTime As TimeSpan = TimeSpan.Parse("17:10:03")
If DateTime.Now.TimeOfDay > dbaseTime Then
Console.WriteLine("Let's go home")
End If
Do everything in your power to convert that string column type to a datetime column.

You can use DateTime.Compare() along with DateTime.Parse() to convert the string to a DateTime object.

DateTime.Parse Will convert the string into a DateTime object which you can then use to compare.

if (DateTime.Now > DateTime.Parse(user_time))
{
...
}
But you really shouldn't store a time as a string, you should use the native time or datetime format of your database, that way you could use the value of the time in your queries, and index them properly.

if (time_now > Date.Parse(DBString)) {
} else {
}