How to check if a DateTime field is not null or empty?

Try following code:

if(!model.myDate.HasValue)
 // do if myDate has null value
else
 // do if myDate has not null value

If you declare a DateTime and initialize with DateTime(), then the default value is DateTime.MinValue, and hence you have to check it like this:

DateTime dat = new DateTime();

if (dat == DateTime.MinValue)
{
   //date is not unassigned
}

If the DateTime is nullable, well that's a different story:

DateTime? dat = null;

if (!dat.HasValue)
{
  //date is not unassigned
}

We can check if a DateTime field is not null or empty using the DateTime? type (nullable DateTime) and its HasValue property.

DateTime? myDateTime = // assume this value is set somewhere
if (myDateTime.HasValue) 
{
    // the DateTime value is not null or empty, so you can use it
    // do something with myDateTime.Value
}

In this example, we are checking if the myDateTime object has a value using the HasValue property. If the property returns true, the DateTime value is not null or empty and you can access it using the Value property.

Alternatively, you can also use the null-coalescing operator (??) to provide a default value in case the DateTime value is null:

DateTime? myDateTime = // assume this value is set somewhere
DateTime defaultDateTime = DateTime.Today; // a default value to use if myDateTime is null

DateTime dateTimeToUse = myDateTime ?? defaultDateTime;

In this example, we are using the null-coalescing operator to assign the value of myDateTime to dateTimeToUse if it is not null, or defaultDateTime if it is null.

Very old post but still valid and helpful.