I am trying to convert datetime? todatetime but I get this Error:
Error 7 Cannot implicitly convert type 'System.DateTime?' to 'System.DateTime'. An explicit conversion exists
Here is my code:
public string ConvertToPersianToShow(DateTime? datetime)
{
DateTime dt;
string date;
dt = datetime;
string year = Convert.ToString(persian_date.GetYear(dt));
string month = Convert.ToString(persian_date.GetMonth(dt));
string day = Convert.ToString(persian_date.GetDayOfMonth(dt));
if (month.Length == 1)
{
month = "0" + Convert.ToString(persian_date.GetMonth(dt));
}
if (day.Length == 1)
{
day = "0" + Convert.ToString(persian_date.GetDayOfMonth(dt));
}
//date = Convert.ToString(persian_date.GetYear(dt)) + "/" +
Convert.ToString(persian_date.GetMonth(dt)) + "/" +
//Convert.ToString(persian_date.GetDayOfMonth(dt));
date = year + "/" + month + "/" + day+"("+dt.Hour+":"+dt.Minute+")";
return date;
}
You have 3 options:
1) Get default value
dt = datetime??DateTime.Now;
it will assign DateTime.Now (or any other value which you want) if datetime is null
2) Check if datetime contains value and if not return empty string
if(!datetime.HasValue) return "";
dt = datetime.Value;
3) Change signature of method to
public string ConvertToPersianToShow(DateTime datetime)
It's all because DateTime? means it's nullable DateTime so before assigning it to DateTime you need to check if it contains value and only then assign.
dt is nullable you need to access its Value
if (datetime.HasValue)
dt = datetime.Value;
It is important to remember that it can be NULL. That is why the nullablestruct has the HasValue property that tells you if it is NULL or not.
You can also use the null-coalescing operator ?? to assign a default value
dt = datetime ?? DateTime.Now;
This will assign the value on the right if the value on the left is NULL
you should be using the .Value of the datetime parameter. All Nullable structs have a value property which returns the concrete type of the object. but you must check to see if it is null beforehand otherwise you will get a runtime error.
i.e:
datetime.Value
but check to see if it has a value first!
if (datetime.HasValue)
{
// work with datetime.Value
}
The problem is that you are passing a nullable type to a non-nullable type.
You can do any of the following solution:
A. Declare your dt as nullable
DateTime? dt = dateTime;
B. Use Value property of the the DateTime? datetime
DateTime dt = datetime.Value;
C. Cast it
DateTime dt = (DateTime) datetime;
Source: Stackoverflow.com