Develop Reference

How can I format a float number so that it looks like real time?

Update! I measure the time like this:
float delta = (float)gameTime.ElapsedGameTime.TotalSeconds;
time += delta;
I want to format a float number so that it looks like this:
minutes:seconds.milliseconds
"0:36.763"
How can I do that?

Your question is vague one, providing that float contains seconds, e.g.
float time = 156.763122f; // 2 minutes (120 seconds) and 36.763122 seconds
You can put (C# 6.0)
string result = $"{(int)time / 60}:{time%60:00.000}";
Or
string result = string.Format(CultureInfo.InvariantCulture,
"{0}:{1:00.000}", (int)time / 60, time % 60);
A better approach, however, is to use TimeSpan which has been designed for that purpose:
TimeSpan ts = TimeSpan.FromSeconds(time);
String result = ts.ToString("m\\:ss\\.fff")

You are using a time span, so you can use a TimeSpan object and make use of its custom formatting:
var timeSpan = TimeSpan.FromSeconds(36.763);
Console.WriteLine(timeSpan.ToString("m\\:ss\\.fff"));
This outputs: 0:36.763
The m specifier denotes single digit minutes, ss denotes double digit secnds and .fff denotes three decimal places of milliseconds.
The \\: is an escape sequence for : and \\. is an escape sequence for ..
You could also write the custom format string as #"m\:ss\.fff"
You can also specify days, hours, minutes, seconds and milliseconds separately if you happen to have the interval represented that way:
var timeSpan = new TimeSpan(0, 0, 0, 36, 763); // (days, hours, mins, secs, ms)

Your question is referring to TimeSpan formatting. If these answers aren't sufficient, you'll find plenty of information using that keyword. I've typically used the following approach.
float time = 75.405f;
TimeSpan TimeInSeconds = TimeSpan.FromSeconds(time);
string StringTime = TimeInSeconds.ToString(#"m\:ss\.fff");
Console.WriteLine(StringTime);
The output of which is
1:15.405
You'll likely want to store your game timer in float seconds. You can convert that to a TimeSpan by specifying from which format you're using (seconds). After that, you can simply convert using the TimeSpan's ToString() method with the correct format specifiers. More information can be found here.
https://msdn.microsoft.com/en-us/library/ee372287(v=vs.110).aspx
By the way, I noticed you've tagged your question as XNA. While XNA is fantastic by all measures, keep in mind that XNA is depreciated and you may want to consider porting to MonoGame or SFML.NET.

Let user specify timer time?

I want the DispatcherTimer to read time values from the textbox : objTextBox.
I tried this code however it seems that TimeSpan is not compatible with strings or did I do anything wrong?
Error: Argument 1: cannot convert from 'string' to 'long'
Also; Does the Time have to look like this in textbox: 0, 0, 1 or 00:00:01?
Code here:
private void testing()
{
string theText = objTextBox.Text;
DispatcherTimer dispatcherTimer = new DispatcherTimer();
dispatcherTimer.Tick += new EventHandler(listjob3_Tick);
dispatcherTimer.Interval = new TimeSpan(theText);
dispatcherTimer.Start();
}

To convert string to TimeSpan, use TimeSpan.Parse(str)

To convert to a TimeSpan from a string you could leverage TimeSpan.Parse, but you'd have to conform to this format [ws][-]{ d | [d.]hh:mm[:ss[.ff]] }[ws] where:
ws is Optional white space.
- is An optional minus sign, which indicates a negative TimeSpan.
d is Days, ranging from 0 to 10675199.
. is A culture-sensitive symbol that separates days from hours. The invariant format uses a period (".") character.
hh is Hours, ranging from 0 to 23.
: is The culture-sensitive time separator symbol. The invariant format uses a colon (":") character.
mm is Minutes, ranging from 0 to 59.
ss is Optional seconds, ranging from 0 to 59.
. is A culture-sensitive symbol that separates seconds from fractions of a second. The invariant format uses a period (".") character.
ff is Optional fractional seconds, consisting of one to seven decimal digits.
so just converting days you could in fact use TimeSpan.Parse and just pass in the string - but if you wanted to convert minutes it would take some massaging of the input like this:
var input = string.Format("00:{0}", objTextBox.Text.PadLeft(2, '0'));
and so then you could issue var timeSpan = TimeSpan.Parse(input); because you've formatted it properly and the Parse will succeed. Another option is to turn minutes into days I guess, but that would require some floating point work and is really, IMO, not as good of an option.

I'm guessing your exception is here:
dispatcherTimer.Interval = new TimeSpan(theText);
Use this instead:
dispatcherTimer.Interval = new TimeSpan(Convert.ToInt64(theText));

#Sneakybastardd: have you read the TimeSpan documentation regarding constructor overloads? You'll note that none of them take string arguments: integer types are required.
After reading the documentation, you might find these TimeSpan methods useful:
Parse()
ParseExact()
TryParse()
With respect to format, See "Standard TimeSpan Format Strings" and "Custom TimeSpan Format Strings". Also do a little research on the various default TimeSpan formats for different cultures if that comes into play at all.

Convert irregular strings to TimeSpan in C#

I have several strings in the format below:
"1:15"
":45"
"1:30:45"
I need them converted to a TimeSpan, but when I TimeSpan.Parse some of them (the first one, for example) it returns it as 1 hour and 15 minutes, where i would want it to be 1 minute and 15 seconds.
Any advice would be greatly appreciated!

You could use an overload of TimeSpan.ParseExact that allows you to specify an array of exact format specifiers.
var formats = new string[] {#"m\:s", #"\:s", ...};
var timeSpace = TimeSpan.ParseExact(input, formats, CultureInfo.CurrentCulture);
Note that ParseExact was introduced in .Net 4

The parameter string needs to be in the specific form specified below:
[ws][-]{ d | [d.]hh:mm[:ss[.ff]] }[ws]
So "1:15" will be treated as hh:mm. If you are passing 1 min 15 seconds, you need to reformat your parameter string to be "00:01:15". You can simply split your string to corresponding days, hour, min, ss variables and use those to assign your TimeSpan object.
MSDN has good documentation here:
http://msdn.microsoft.com/en-us/library/se73z7b9.aspx

Briefest way to display TimeSpan value as an elapsed time e.g. 1:45:33

I'd like an easy way to display any TimeSpan as an elapsed time without using loops or custom logic
e.g.
hours : minutes : seconds
I'm sure there must be a .NET built-in or format string that applies, however I'm unable to locate it.

The question itself isn't a duplicate but the answer, I assume, is what you are looking for - Custom format Timespan with String.Format. To simplify your solution further you could wrap that functionality up in an extension method of Timespan.

What's wrong with TimeSpan.ToString()?
EDIT: You can use a DateTime as an intermediate formatting store:
TimeSpan a = new TimeSpan(1, 45, 33);
string s = string.Format("{0:H:mm:ss}", new DateTime(a.Ticks));
Console.WriteLine(s);
Not pretty but works.

You can use:
TimeSpan t = TimeSpan.FromSeconds(999);
string s = t.ToString("c"); // s = "00:16:39"
For custom formats, see this MSDN page.

Here is a method I use for custom formatting:
TimeSpan Elapsed = TimeSpan.FromSeconds(5025);
string Formatted = String.Format("{0:0}:{1:00}:{2:00}",
Math.Floor(Elapsed.TotalHours), Elapsed.Minutes, Elapsed.Seconds);
// result: "1:23:45"
I don't know if that qualifies as "without custom logic," but it is .NET 3.5 compatible and doesn't involve a loop.

Use This: .ToString()
According to MSDN, the default format this displays is [-][d.]hh:mm:ss[.fffffff]. This is the quickest and easiest way to display TimeSpan value as an elapsed time e.g. 1:45:33
If you have days, fractions of a second, or a negative value, use a custom format string as described in MSDN. This would look like .ToString(#"hh\:mm\:ss")
Example:
TimeSpan elapsed = new TimeSpan(0, 1, 45, 33);
Console.WriteLine(elapsed.ToString()); //outputs: "1:45:33"
Console.WriteLine(elapsed.ToString(#"hh\:mm\:ss"));//outputs: "1:45:33"

C# + Format TimeSpan

I am trying to format a TimeSpan element in the format of "[minutes]:[seconds]". In this format, 2 minutes and 8 seconds would look like "02:08". I have tried a variety of options with String.Format and the ToString methods, but I get a FormatException. This is what I'm currently trying:
DateTime startTime = DateTime.Now;
// Do Stuff
TimeSpan duration = DateTime.Now.Subtract(startTime);
Console.WriteLine("[paragraph of information] Total Duration: " + duration.ToString("mm:ss"));
What am I doing wrong? How do I format a TimeSpan element using my desired format?

NOTE: This answer applies to .NET 4.0 only.
The colon character is a literal and needs to be wrapped in single quotes:
duration.ToString("mm':'ss")
From the MSDN documentation:
The custom TimeSpan format specifiers
do not include placeholder separator
symbols, such as the symbols that
separate days from hours, hours from
minutes, or seconds from fractional
seconds. Instead, these symbols must
be included in the custom format
string as string literals.

Try this:
Console.WriteLine("{0:D2}:{1:D2}", duration.Minutes, duration.Seconds);

Custom formatting of System.TimeSpan was added in .Net 4, so you can now do the following:
string.Format("{0:mm\\:ss}", myTimeSpan);
(UPDATE) and here is an example using C# 6 string interpolation:
$"{myTimeSpan:hh\\:mm\\:ss}"; //example output 15:36:15
In short you now need to escape the ":" character with a "\" (which itself must be escaped unless you're using a verbatim string).
This excerpt from the MSDN Custom TimeSpan Format Strings page explains about escaping the ":" and "." charecters in a format string:
The custom TimeSpan format specifiers do not include placeholder separator symbols, such as the symbols that separate days from hours, hours from minutes, or seconds from fractional seconds. Instead, these symbols must be included in the custom format string as string literals. For example, "dd.hh:mm" defines a period (.) as the separator between days and hours, and a colon (:) as the separator between hours and minutes.

For some mysterious reason TimeSpan never got the ToString() overloads that support formatting until .NET 4.0. For earlier releases, as long as it is positive, you can hijack DateTime.ToString():
TimeSpan ts = new TimeSpan(0, 2, 8);
string s = new DateTime(ts.Ticks).ToString("mm:ss");

The date and time format strings only apply to DateTime and DateTimeOffset. Yo can use a normal format string, though:
string.Format("{0}:{1:00}", Math.Truncate(duration.TotalMinutes), duration.Seconds)
Note that using TotalMinutes here ensures that the result is still correct when it took longer than 60 minutes.

Try this:
DateTime startTime = DateTime.Now;
// Do Stuff
TimeSpan duration = DateTime.Now.Subtract(startTime);
Console.WriteLine("[paragraph of information] Total Duration: " + duration.Minutes.ToString("00") + ":" + duration.Seconds.ToString("00"));

Based on this MSDN page describing the ToString method of TimeSpan, I'm somewhat surprised that you can even compile the code above. TimeSpan doesn't have a ToString() overload that accepts only one string.
The article also shows a function you can coyp and use for formatting a TimeSpan.

you could always do:
string.Format("{0}:{1}", duration.Minutes, duration.Seconds);

You can use the below code.
TimeSpan tSpan = TimeSpan.FromSeconds(allTotalInMinutes);
string tTime = string.Format("{1:D2}:{2:D2}", tSpan.Minutes, tSpan.Seconds);
It will show ie 34:45 format.
Hope it will help you.

TimeSpan t = TimeSpan.Parse("13:45:43");
Console.WriteLine(#"Timespan is {0}", String.Format(#"{0:yy\:MM\:dd\:hh\:mm\:ss}", t));