DataTimePicker databinding vs nullable DateTime

I just came across an interesting problem. You can't bind a nullable dateTime directly to a dateTimePicker. At least not easily. Here's an extension method that handles the heavy lifting.

/// <summary>

/// 

/// </summary>

/// <param name="dtp"></param>

/// <param name="dataSource"></param>

/// <param name="valueMember"></param>

/// <remarks>With help from Dan Hanan at http://blogs.interknowlogy.com/danhanan/archive/2007/01/21/10847.aspx</remarks>

public static void BindNullableValue(this DateTimePicker dateTimePicker, BindingSource dataSource, String valueMember)

{

var binding = new Binding("Value", dataSource, valueMember, true);

//OBJECT PROPERTY --> CONTROL VALUE

binding.Format += new ConvertEventHandler((sender, e) =>

{

Binding b = sender as Binding;

if (b != null)

{

DateTimePicker dtp = (binding.Control as DateTimePicker);

if (dtp != null)

{

if (e.Value == null)

{

dtp.ShowCheckBox = true;

dtp.Checked = false;

// have to set e.Value to SOMETHING, since it's coming in as NULL

// if i set to DateTime.Today, and that's DIFFERENT than the control's current

// value, then it triggers a CHANGE to the value, which CHECKS the box (not ok)

// the trick - set e.Value to whatever value the control currently has. 

// This does NOT cause a CHANGE, and the checkbox stays OFF.

e.Value = dtp.Value;

}

else

{

dtp.ShowCheckBox = true;

dtp.Checked = true;

// leave e.Value unchanged - it's not null, so the DTP is fine with it.

}

}

}

});

// CONTROL VALUE --> OBJECT PROPERTY

binding.Parse += new ConvertEventHandler((sender, e) => {

// e.value is the formatted value coming from the control. 

// we change it to be the value we want to stuff in the object.

Binding b = sender as Binding;

if (b != null)

{

DateTimePicker dtp = (b.Control as DateTimePicker);

if (dtp != null)

{

if (dtp.Checked == false)

{

dtp.ShowCheckBox = true;

dtp.Checked = false;

e.Value = (Nullable<DateTime>) null;

}

else

{

DateTime val = Convert.ToDateTime(e.Value);

e.Value =val;

}

}

}

});

dateTimePicker.DataBindings.Add(binding);

}