C# DateTime to null

How to set DateTime to null in C#

You can solve this problem in two ways, either make it a nullable type, or use the System.DateTime.MinValue.

C# Nullable Type

When a type can be assigned null is called nullable, that means the type has no value. All Reference Types are nullable by default, e.g. String, and all ValueTypes are not, e.g. Int32. The Nullable < T > structure is using a value type as a nullable type.

By default DateTime is not nullable because it is a Value Type, using the nullable operator introduced in C# 2, you can achieve this.

Using a question mark (?) after the type or using the generic style Nullable.

Nullable < DateTime > nullDateTime;

or

DateTime? nullDateTime = null; 

using System;
using System.Text;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            Nullable nullDateTime;
            //DateTime? nullDateTime = null;
            nullDateTime = DateTime.Now;
            if (nullDateTime != null)
            {
                MessageBox.Show(nullDateTime.Value.ToString());
            }
        }
    }
}

Convert String to DateTime

In .Net, you can work with date and time easy with the DateTime class. You can use the methods like Convert.ToDateTime(String), DateTime.Parse() and DateTime.ParseExact() methods for converting a string-based date to a System.DateTime object. More about..... String to DateTime

DateTimePicker Control

The DateTimePicker control has two parts, a label that displays the selected date and a popup calendar that allows users to select a new date. The most important property of the DateTimePicker is the Value property, which holds the selected date and time. More about..... DateTimePicker

How to find date difference ?

A calculation using a DateTime structure, such as Add or Subtract, does not modify the value of the structure. Instead, the calculation returns a new DateTime structure whose value is the result of the calculation. The DateTime.Substract method may be used in order to find the date-time difference between two instances of the DateTime method. More about..... Find date difference