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How can I store a formatted DateTime into column of type DateTime in Database?

I'm retrieving data from the database in a dataset and printing it in a pdfdocument. One table has got a DateTime column and the value comes as "12/27/2018 12:00:00 AM". I'm trying to format that as dd/MM/yyyy but with no success since it is expecting a DateTime and formatting return a string value. Should I change the column datatype or there is a way to maintain it and format the datetime?

I recommend changing the database from string to DateTime. But if you cannot you can use something like this
DataTable dt1 = new DataTable();
DataTable dt2 = dt1.Clone();
//change columns type
dt2.Columns["Col A"].DataType = typeof(DateTime);
int colNumber = dt2.Columns.IndexOf("Col A");
foreach (DataRow row in dt1.AsEnumerable())
{
object[] rowData = row.ItemArray;
rowData[colNumber] = DateTime.Parse(row.Field<string>("Col A"));
dt2.Rows.Add(rowData);
}

How to update first column of a datatable for all rows using LINQQ or any other method?

I have a data table with 4 columns datetime,id, message & status. I want to update the datetime column with a new datetime (updated datetime is in different time zone, from CST to UTC). First I was thinking to do it like I would take the datetime column and store it in a list and convert the list to utc time zone from cst.Then add the list to the same table and rearrange the columns. But this sounds stupid so is there any way to update the existing value with new values for one column of datatable.
I found the below code in one of the posts but not sure what exactly is happening.
var rowsToUpdate =
dt.AsEnumerable().Where(r => r.Field<string>("datetime") == datetime);
foreach(var row in rowsToUpdate)
{
row.SetField("datetime", utcDate);
}
The data in datatable is in CST timezone but I want that timezone to be converted to UTC timezone and update the table.
List<DateTime> lstCST = new List<DateTime>();
lstCST = datatable.AsEnumerable().Select(r=>r.Field<DateTime>("CSTDatetime")).ToList();
List<DateTime> lstUTC = new List<DateTime>();
DateTime dt = DateTime.Now;
foreach(var v in lstCST )
{
dt= TimeZoneInfo.ConvertTimeToUtc(v);
lstUTC.Add(dt);
}
Can anybody point me in the right direction on how to do this.

If you want to update all rows you don't need LINQ but TimeZoneInfo.ConvertTimeToUtc:
TimeZoneInfo cstZone = TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time");
foreach (DataRow row in dataTable.Rows)
{
DateTime cstDateTime = row.Field<DateTime>("CSTDatetime");
DateTime utcDateTime = TimeZoneInfo.ConvertTimeToUtc(cstDateTime, cstZone);
row.SetField("CSTDatetime", utcDateTime);
}

Look at this example:
DataTable table = new DataTable();
table.Columns.AddRange(new DataColumn[]
{
new DataColumn(),
new DataColumn(),
new DataColumn()
});
table.Rows.Add(1, 2, 3);
foreach (DataRow dr in table.Rows)
{
dr[0] = 99;
}
it will update all rows of the first column and set it to 99

To explain what the snippet does:
This is a filter:
var rowsToUpdate =
dt.AsEnumerable().Where(r => r.Field<string>("datetime") == datetime);
It selects all rows where the "datetime" column has a specific value. In your case, I guess you can ignore this, you want to do this on all rows.
So instead of iterating on the filtered rows, iterate all rows.
foreach(var row in rowsToUpdate)
{
row.SetField("datetime", utcDate);
}
The latter snippet sets the "datetime" value in each row of the selection to the value of utcDate. In your case, just replace this by first getting the "old" value, convert it and then use the above line to set the converted value.
#TimSchmelter already gave a ready-to-go solution so I won't repeat it. I rather wanted to explain what was seemingly unclear to you.

how can I format this string to MM/dd/yyyy

I have tried a lot of syntax but I can't get it work,
from my DataTable i have this values , please see below
the above values are from the jQuery datepicker, I just make them values in my query.
C#:
I catch the values from the datepicker using this parameter`
List<DateTime> WeekDates
how can i make it to display as 1/6/2016 . thank you for any help!
foreach (DataRow row in dt.Rows)
{
Sale sales = new Sales();
sale.WeekStart = row["WeekStart"].ToString("MM/dd/yyyy");
}
UPDATE
is my date values are string or a DateTime already? I catch the values in my webmethod using this
List<DateTime> WeekDates, but when it comes to my dataTable it has a single quotes , notice it.

Try
foreach (DataRow row in dt.Rows)
{
Sale sales = new Sales();
var date = Convert.ToDateTime(row["WeekStart"]);
sale.WeekStart = date.ToString("MM/dd/yyyy"); // If sale.WeekStart field is string
}
Complete description: http://www.csharp-examples.net/string-format-datetime/

[YourDateTimeVarialble].ToString("MM/dd/yyyy");

[date].ToString("MM/dd/yyyy");
you can use this one

Have you tried
sale.WeekStart =DateTime.Parse(row["WeekStart"].ToString()).ToString("MM/dd/yyyy");
I think this is work for you

Try
(DateTime.ParseExact(row["WeekStart"]), "M/d/YYYY hh:mm:SS tt", System.Globalization.CultureInfo.InvariantCulture)).ToString("MM/dd/yyyy");

If those values came from a database, you may want to format them first before populating to your DataTable. For your desired format, you may refer to this post.
Update 1
Try formatting your jQuery DatePicker to something like:
$(".selector").datepicker({ dateFormat: "MM/dd/yyyy" });
Update 2
foreach (DataRow row in dt.Rows)
{
Sale sales = new Sales();
sale.WeekStart = Convert.ToDateTime(row["WeekStart"]).ToString("MM/dd/yyyy");
}

Try something like this
string date = "1/6/2016 12:00:00 AM";
string d = Convert.ToDateTime(date).ToShortDateString();
O/P : 1/6/2016
In your case perhaps following code will be useful
DataTable dt = new DataTable();
dt.Columns.Add("Date");
DataRow row1 = dt.NewRow();
row1["Date"] = "1/6/2016 12:00:00 AM";
dt.Rows.Add(row1);
DataRow row2 = dt.NewRow();
row2["Date"] = "2/6/2016 12:00:00 AM";
dt.Rows.Add(row2);
List<string> WeekStart = new List<string>();
foreach (DataRow row in dt.Rows)
{
WeekStart.Add(Convert.ToDateTime(row["Date"]).ToShortDateString());
}

try this
string text = row["Weekstart"].ToString();
DateTime date = DateTime.ParseExact(text, "dd/MM/yyyy", null);

Thank you for all who answered my question. As for now the quick solution for me is to remove unnecessary string to display the format MM/dd/yyyy
using this syntax
row["WeekStart"].ToString().Remove(9);
Most of you answered the correct syntax to convert it to the MM/dd/yyyy but I figured out that the values of dates from my jQuery datepicker has a single quote value, what I did is removed it before feeding to my SQL parameters and everything works fine. I already used that syntax before I post here , I just need to remove the single quote in my datetime values.

How to remove time from datetime column in dataset?

I have to export data to excel sheet in asp.net c# application. Now I have wriiten below lines of code
DataTable dt = new DataTable();
dt = ds.Tables[0];
foreach (DataRow row in dt.Rows)
{
row["ExpiryDate"] = Convert.ToDateTime(row["ExpiryDate"]).ToShortDateString();
}
DataSet dsn = new DataSet();
DataTable dtcopy = dt.Clone();
dsn.Tables.Add(dtcopy);
WebUtility.GenrateExcel(ds, "ExpiredDocuments");
I want to first remove time from data set's Expiry date column and then pass
it to the generate Excel function so that time will not appear in Expiry date column in excel... Please help the above code is not working...

I guess, you need look through this:
https://msdn.microsoft.com/en-us/library/8kb3ddd4(v=vs.110).aspx
You should use smth like
Convert.ToDateTime(ds.Tables[0].Rows[i]["ExpiryDate"]).ToString("MM/dd/yyyy")
Or whatever you need.

These are the steps you need to do in order to accomplish what you are asking:
Create a new column of type string
Set the new column's value to ShortDateString of the corresponding "ExpiryDate" column
Remove the "ExpiryDate" column
Move the new string column to the position of the old "ExpiryDate" column
Rename the new column to "ExpiryDate"
Like so:
dt.Columns.Add("ExpiryDateString", typeof(String));
foreach(DataRow row in dt.Rows)
{
row["ExpiryDateString"] = ((DateTime)row["ExpiryDate"]).ToShortDateString();
}
int columnNumber = dt.Columns["ExpiryDate"].Ordinal;
dt.Columns.Remove("ExpiryDate");
dt.Columns["ExpiryDateString"].SetOrdinal(columnNumber);
dt.Columns["ExpiryDateString"].ColumnName = "ExpiryDate";

field<t> invalid cast

I'm having problems when using linq on a datatable.asenumerable().
This throws InvalidCastException.
DateTime date=r.Field<DateTime>("date");
This works fine.
DateTime date = DateTime.Parse(r.Field<string>("date"));
What am I missing?
Regards Sven

Why would you expect it to work? The following code doesn't compile:
DateTime dt1 = (DateTime)"2004-01-01";
Whereas this does:
DateTime dt1 = DateTime.Parse("2004-01-01");
As in, you can't just cast a string to a DateTime, so if your value is a string, you need to explicitly convert it.

Are you sure your "date" column is of type DateTime?
This test code works as expected:
DataTable dt = new DataTable();
dt.Columns.Add(new DataColumn("date", typeof(DateTime)));
for (int i = 0; i < 10; i++)
{
DataRow row = dt.NewRow();
row["date"] = DateTime.Now.AddDays(i);
dt.Rows.Add(row);
}
foreach (var r in dt.AsEnumerable())
{
DateTime d = r.Field<DateTime>("date"); // no problems here!
Console.Write(d.ToLongDateString());
}

Cast works between related types. string and date don't belong to same hierarchy & hence no direct translation is possible.
You can use cast, when you are sure that the types are related and conversion is possible.
Parse is different than cast.
i.e you are telling the runtime to see if it can be parsed to make a date out of it (per your example).