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How do I extract the day from this DateTime variable?

I want to extract the name of the day as string from this:
Holder.CurrentDate = DateTime.Now.AddDays(countNext).ToLongDateString();
Holder.CurrentDay = ?
Where Holder.CurrentDay is a string. I have tried:
Holder.CurrentDay = Holder.CurrentDate.DayOfWeek.ToString();
But DayOfWeek does not exist as a function in this context. Do you guys have any ideas how I can accomplish this?

You could just do this:
var CurrentDate = DateTime.Now.AddDays( 4 ).ToLongDateString();
var CurrentDay = Convert.ToDateTime(CurrentDate).DayOfWeek.ToString();
But its better to store the DateTime itself in a variable instead of converting it back:
var theDateWeNeed = DateTime.Now.AddDays( 4 );
//Now we can do this:
Holder.CurrentDate = theDateWeNeed.ToLongDateString();
Holder.CurrentDay = theDateWeNeed.DayOfWeek.ToString();

You would be better to use ToString with a format pattern if what you ultimately want is a string. Then you have control over language, etc.
Use the "dddd" pattern to get the name of the day of the week.
var dayOfWeek = DateTime.Now.ToString("dddd");
Pass a second CultureInfo parameter if you want it in a specific language.

I found a way, sorry...
Holder.CurrentDay = DateTime.Now.AddDays(countNext).DayOfWeek.ToString();

You cannot invoke DayOfWeek on string. i.e. you have to convert it back or use the same DateTime as you did in your previous statement.
Holder.CurrentDay = DateTime.Now.AddDays(countNext).DayOfWeek.ToString();

Remove '0' (Number) from DateTime Month and Day (String)

Can anybody tell me the best approach or solution on how I would do the following?
I have a DateTime (as String) in following format:
string test = "21.12.2013";
How could I now remove all zero's from the month and day but still 'keep' the DateTime Logic:
//Example 1
string input = "06.10.2013" // 6th October
string output = "6.10.2013" //only remove '0' from the day
//Example 2
string input = "01.09.2012" // 1st September
string output = "1.9.2012" //remove from month and day
//Example 3
string input = "20.10.2011" // 20th October
string output = "20.10.2011" //should (must) stay!
I can also parse to DateTime if that would be make it easier but yeah I hope you got my idea...
Any help appreciated!

Parsing your string into DateTime and getting it back to string using ToString with desired patter seems to be the easiest way to go:
public static string GetRidOfZeros(string input)
{
var dt = DateTime.ParseExact(input, "dd.MM.yyyy", CultureInfo.InvariantCulture);
return dt.ToString("d.M.yyyy", CultureInfo.InvariantCulture);
}
Little testing, with your sample data:
var inputs = new List<string> { "06.10.2013", "01.09.2012", "20.10.2011" };
var outputs = new List<string> { "6.10.2013", "1.9.2012","20.10.2011" };
if(outputs.SequenceEqual(inputs.Select(d => GetRidOfZeros(d))))
Console.WriteLine("Output is OK");
else
Console.WriteLine("Collections does not match.");
Prints Output is OK.

DateTime.Parse(input).ToString("d.M.yyyy")

As you said, parsing to DateTime first would probably make things easier, since then you can just use:
myDateTime.ToString("d.M.yyyy");

When you parse it you can use ToString to format it any way you like:
var date = "06.10.2013";
DateTime parsed = DateTime.ParseExact(date, "dd.MM.yyyy", CultureInfo.InvariantCulture);
var noZerosHere = parsed.ToString("d.MM.yyyy");

A decent "catch-all" method (that will work not just on DateTime but ANY kind of string) would be to split the string up, take out leading zeroes and then put the pieces back together again.
string input = "01.09.2012";
string[] values = input.Split(".");
string[] modifiedValues = values.Select(x => x.TrimStart('0');
string output = String.Join(".", modifiedValues);
You can adjust the delimiters for different representations of DateTime, e.g. those that use slashes (01/09/2012) or are written in a different order.

Join date and time strings into a DateTime

Given two strings with the following values:
31/05/2013 0:00:00
21:22
What's the most efficient way to join them into a DateTime data type to get:
31/05/2013 21:22
The time portion of the first string "0:00:00" is ignored, in favor of using the "time" from the second string.

Use a TimeSpan object and DateTime.Add(yourTimeSpan); e.g.
DateTime dt = new DateTime(2013,05,31);
var dts = dt.Add(new TimeSpan(0, 21, 22, 0, 0));
Extending the answer a bit, you can parse the date and time first, e.g.
DateTime dt = DateTime.Parse("05/31/2013 0:00:00");
TimeSpan ts = TimeSpan.Parse("21:22");
var dts = dt.Add(ts);
...keep in mind, I am not checking for bad date/time values. If you're unsure if the values are real dates/times, use DateTime.TryParse and handle appropriately.

As #George said, parse the first value as a DateTime and then another one as TimeSpan and then add the TimeSpan to first parsed value.
Another option is getting the substring of first 10 charachters of first value and concat it with a space with second value and parse it as DateTime.

Say that the first string is called one and the second one is called two, just do this:
DateTime result = DateTime.Parse(one).Date + DateTime.Parse(two).TimeOfDay;

string strDate = "31/05/2013 0:00";
string strTime = "21:22";
strDate = strDate.Replace("0:00", strTime);
DateTime date = Convert.ToDateTime(strDate);

If you are really dealing with only strings, then:
string strDate = "31/05/2013 0:00:00";
string strTime = "21:22";
string strDateTime = strDate.Split(' ')[0] + " " + strTime;

If you can safely assume you are getting 2 digit month and day, a 4 digit year, and a space after the date:
var date = "31/05/2013 0:00:00";
var time = "21:22";
var dateTime = DateTime.Parse(date.Substring(0,11) + time);
If the assumptions about the input format aren't solid you could use a regex to extract the date instead of Substring.

If you're starting out with just strings, you can just do this:
var dateString = "31/05/2013 00:00";
var timeString = "21:22";
var dateTimeString = dateString.Substring(0, 11) + timeString;
var output = DateTime.ParseExact(dateTimeString, "dd/MM/yyyy HH:mm", null);
Assuming you know for sure this format won't change (a dangerous assumption, to be sure), this will work. Otherwise, you'd have to parse the date and time strings separately and use conventional date manipulation as others suggested. For example:
var ci = System.Globalization.CultureInfo.CreateSpecificCulture("en-GB");
var dateString = "31/05/2013 00:00";
var timeString = "21:22";
var output = DateTime.Parse(dateString, ci) + TimeSpan.Parse(timeString, ci);

DateTime date = DateTime.ParseExact("31/05/2013 0:00:00", "dd/MM/yyyy h:mm:ss", CultureInfo.InvariantCulture);
TimeSpan span = TimeSpan.ParseExact("21:22", "t", CultureInfo.InvariantCulture);
DateTime result = date + span;

Find highest DateTime from list of DateTime's

My Question is that, I want to find the highest DateTime from a list of DateTime?
I have one Array suppose string[] btime = new string[100];
In that Array I am storing the Date which is coming from the SQL-Server
The SQL Query is [CONVERT(varchar(10),GETDATE(),101)] it is returning the Date in format of MM/dd/yyyy
and then after I am concatenating the Date with my own given Time
i.e .btime[j] = SqlServerDate + " " + 15:20; and so on;
Now, from this given Array I want to find highest Date and Time
So, I have use this logic
string large=""
large=btime[0];
for (int i = 0; i < j; i++)
{
if (DateTime.Compare(DateTime.Parse(btime[i]),DateTime.Parse(large)) > 0)
{
large = btime[i];
}
}
but I am getting the Error at
if(DateTime.Compare(DateTime.Parse(btime[i]),DateTime.Parse(large)) > 0)
The Error is String not recognized as valid DateTime This error is occurring because of my System DateTime Format is yyyy/dd/MM
So Plz any one can help me in solving this problem
I don't want to change format of the system

Others have suggested different ways of parsing the DateTime. This seems pointless to me - if you can possibly change the query, just avoid performing the conversion to a string in the first place. The fewer conversions you use, the fewer chances you have for this sort of thing to be a problem.
Change the query so you end up with DateTime values, and then finding the latest one is trivial in LINQ:
DateTime latest = dateTimes.Max();

Hum,
// Containing your datetime field
string[] btime = new string[100];
var max = btime.Select(s => DateTime.Parse(s, "MM/dd/yyyy", CultureInfo.InvariantCulture)).Max();

Use the DateTime.ParseExact Method.
Example:
CultureProvider provider = CultureInfo.InvariantCulture;
DateTime.ParseExact(btime[i], "yyyy/dd/MM", provider);

you, can use DateTime.ParseExact() functionality to do this. Refer the following code part.
CurDate = DateTime.ParseExact(Name3, "yyyyMMddhhmmssffff", System.Globalization.CultureInfo.CurrentCulture, System.Globalization.DateTimeStyles.None)

You can use the DateTime.ParseExact() method.
CultureProvider provider = CultureInfo.InvariantCulture;
DateTime.ParseExact(btime[i], "MM/dd/yyyy HH:mm", provider);
The second parameter there is the format string. This specifies how your date will be formatted.
Since you are adding a 24 hour time at the end you need the HH:mm (HH says expect a 24 hour time).

Thanks to everyone.
I have got some sort of answer:
string large = "";
large = btime[0];
IFormatProvider culture = System.Threading.Thread.CurrentThread.CurrentCulture;
// This Code will convert the System Format in Thread, Not the Actual Format
// of The System
CultureInfo ciNewFormat = new CultureInfo(CultureInfo.CurrentCulture.ToString());
ciNewFormat.DateTimeFormat.ShortDatePattern = "MM/dd/yyyy";
System.Threading.Thread.CurrentThread.CurrentCulture = ciNewFormat;
for (int i = 0; i < TimeBackupCounter; i++)
{
if (DateTime.Compare(DateTime.Parse(btime[i]),DateTime.Parse(large)) > 0)
{
large = btime[i];
}
}

How to convert a date of integers to a formated date string (i.e. 2012009 to 2/01/2009)

Any ideas?
I can't come up with any.
I have a list of dates I'm loading in from a csv file and they are saved as all integers, or rather a string of integers (i.e. Jan 1, 2009 = 1012009)
Any ideas on how to turn 1012009 into 1/01/2009?
Thanks!

Since the date is stored as a string, you may want to use ParseExact:
DateTime date = DateTime.ParseExact("28012009", "dMMyyyy", null);
ParseExact will throw an exception if the format doesn't match. It has other overloads, where you can specify more than a single possible format, if that is required. Note that here provider is null, which uses the current culture.
Depending on style you may wish to use TryParseExact.

int date = 1012009;
var month = date / 1000000;
var day = (date / 10000) % 100;
var year = date % 10000;
var formatted = new DateTime(year, month, day).ToString();
This assumes month-day-year; if the numbers are day-month-year, I’m sure you’ll be able to swap the month and day variables to accommodate that.
If you want to customise the date format, you can do so as described in:
Standard Date and Time Format Strings
Custom Date and Time Format Strings

Let 10102009 be dateInt.
string dateString = dateInt.ToString();
int l = dateString.Length;
dateString = dateString.Insert(l-3,"/");
dateString = dateString.Insert(l-6,"/");
You should now have 1/01/2009 in dateString.. You can also try the ParseExact function..