How to open DateTime picker C# control programmatically on Button Click

You have to use interop to to send request to windows that show DataTimePicker 
on click of the button

?

//include namespace section using System.Runtime.InteropServices;   //declares [DllImport("user32.dll")] private static extern bool PostMessageForCalender( IntPtr hWnd, // handle to destination window Int32 msg, // message Int32 wParam, // first message parameter Int32 lParam // second message parameter );   const Int32 WM_LBUTTONDOWN = 0x0201;   //method to call  calender dropdown private void button1_Click(object sender, EventArgs e) {     Int32 x = dateTimePicker1.Width - 10;     Int32 y = dateTimePicker1.Height / 2;     Int32 lParam = x + y * 0x00010000;       PostMessageForCalender(dateTimePicker1.Handle, WM_LBUTTONDOWN, 1,lParam);   }