How to initialize DateTimePicker to null

Question

Hello,

how can i initialize a DateTimePicker to null when i have data binding as well?
I found the following example, i added the .cs file to my project but i don't know what to do from that point forward.
http://www.codeproject.com/KB/selection/Nullable_DateTimePicker.aspx

Any suggestions? (even with this example or another one)

Thank you in advance.

Nir Bar · Answer

Hi Dealy, There is a trick you can do that worked perfectly for me. Unfortunately I don't have the code with me, but I can give you the idea: DataTimePicker has a check-box that can be used to disable date selection. To enable it you should set ShowCheckBox to true. You should derive from DateTimePicker and create a new property called "NullableValue" of type object The new property should return null if the CheckBox is unchecked, and return Value is the CheckBox is checked. When setting the NullableValue to a valid DateTime, then the CheckBox should be checked When setting it to null, then set CheckBox to unchecked Also, to better support DataBinding, you should create an event called NullableValueChanged, that will fire on every change public object NullableValue { get { if (!Checked) { return null; } return Value; } set { if ((value == null) || (value == DBNull.Value)) { OnNullableValueChanged(new EventArgs()); Checked = false; } else { Checked = true; Value = (DateTime)value; } } } Please mark this post as an answer if it helps you Nir

Dealy · Answer

The thing is that i tried to use the first example with customized DateTimePicker and override the default, but i didn't managed to make it work. So i was wondering if someone knows how this works to show me. Thank you though for your time.

Dushan Stankovic · Answer

Then you must create your own DateTimePicker class using TextBox class. I was thinking that you wanted to clear Text prop of DateTimePicker. Because you want that Value prop have a null val you must create in you new class prop Value of Nullable type.

Dealy · Answer

Thank you for trying to help me. I try the code as you suggested but i still don't get " " value. I get the dateTimePicker1.Value which is todays date.

Dushan Stankovic · Answer

My friend I find solution. Firs you must set to a prop CustomFormat value " ", blanko. In Properties win just press space in that prop. Look this code: public partial class Form2 : Form { private DateTimePickerFormat dtpf; public Form2() { InitializeComponent(); this.dtpf = this.dateTimePicker1.Format; } private void button1_Click(object sender, EventArgs e) { this.dateTimePicker1.Format = DateTimePickerFormat.Custom; } private void dateTimePicker1_CloseUp(object sender, EventArgs e) { this.dateTimePicker1.Format = this.dtpf; } private void dateTimePicker1_FormatChanged(object sender, EventArgs e) { if (this.dateTimePicker1.Format != DateTimePickerFormat.Custom) this.dtpf = this.dateTimePicker1.Format; } } I think that you will understand what I did.

Dushan Stankovic · Answer

DateTimePicker control is reference type, and it can be null referenced. But Value prop of the DateTimePicker is of the DateTime type, and it is value type. It means that it can't have null value. If you want to value types have null value it must be declared with System.Nullable class. You can't do that with DateTimePicker control because it's Value prop is declared like DateTime. I propose you to create your own Custom control using TextBox control and create DateTimePicker control with reference DateTime type and it own behavior. Or, create new class inherited form DateTimePicker class and override OnPaint and change other stuffs. This second way I can't help you but you can make a new post for that.

Dealy · Answer

When user clicks on add new record i want the DateTimePicker fields to be blank not to have the value of MinDate plus if user tries to update i DateTimePicker that already has a value to have the choice of null value as well.

Trinity · Answer

Do you want when a certain data is selected then it is saved as null in the data base? or am I wrong?