I created a VS 2010 project with the default form. Below is the complete text of the form constructor. The RadDateTimePicker code is what was generated when the control was added to a form.
dtmCompletedAt = new RadDateTimePicker();
dtmCompletedAt.CustomFormat = "h:mm tt";
dtmCompletedAt.Format = System.Windows.Forms.DateTimePickerFormat.Custom;
dtmCompletedAt.Location = new System.Drawing.Point(10, 10);
dtmCompletedAt.MaxDate = new System.DateTime(2099, 12, 31, 0, 0, 0, 0);
dtmCompletedAt.MinDate = new System.DateTime(2000, 1, 1, 0, 0, 0, 0);
dtmCompletedAt.Name = "dtmCompletedAt";
dtmCompletedAt.NullDate = new System.DateTime(2000, 1, 1, 0, 0, 0, 0);
dtmCompletedAt.NullText = "Select...";
dtmCompletedAt.ShowUpDown = true;
dtmCompletedAt.Size = new System.Drawing.Size(150, 20);
dtmCompletedAt.Value = new System.DateTime(2000, 1, 1, 0, 0, 0, 0);
My expectation is that since the Value of the DateTimePicker is set to the NullDate value, and also SetToNullValue() has been called, the the DateTimePicker will display the NullText. However, the DateTimePicker actually displays an empty text box.
While putting this sample together I discovered that the problem is actually related to setting ShowUpDown=true, which seems to be recommended for a TimePicker. Setting it to false does cause the NullText to display; but it also shows the calendar drop down, which is not appropriate for a time picker.
I guess the revised question should be:
How do I get the NullText to appear for a TimePicker, and not also show the drop down calendar? Having the spin buttons would be nice, but is not a requirement.