if datetime is not null in csharp

You can use an if statement along with the DateTime? type (nullable DateTime) to check if a DateTime variable has a value or it is null. Here's an example:

main.cs
DateTime? myDateTime = null; // The variable is nullable, so it can store a null value

if (myDateTime.HasValue)
{
    Console.WriteLine("The DateTime variable has a value: " + myDateTime.Value);
}
else
{
    Console.WriteLine("The DateTime variable is null.");
}
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In the above code, the if statement checks if the myDateTime variable has a value by invoking the HasValue property. If the variable contains a valid DateTime value, the if block will be executed, otherwise the else block will execute, indicating that the DateTime variable is null.