You cannot convert a dbnull to a date. Try changing the Initialize Control procedure to this.

i gotit. nw the problem is that the cell 5 and 6 of my datagridview are calendercolumns. whenever i run the program and exit, the calendercolumns are resetting to postions 0 and 1. i mean the column 0 and column 1 of datagridview are coming as calendercolumn. it is resetting by itself. i didn't add any such codes. even if i am running some other forms of the project it is resetting.

can anybody tell me why

Just wanted to mention that the code for How to: Host Controls in Windows Forms DataGridView Cells is up to date and includes a line that is missing from the above code. The InitializeEditingControl implementation should be:

    public override void InitializeEditingControl(int rowIndex, object
        initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)
    {
        // Set the value of the editing control to the current cell value.
        base.InitializeEditingControl(rowIndex, initialFormattedValue,
            dataGridViewCellStyle);
        CalendarEditingControl ctl =
            DataGridView.EditingControl as CalendarEditingControl;
        ctl.Value = (DateTime)this.Value;
    } 

The last line ensures that the hosted DateTimePicker gets the current cell value when the cell enters edit mode.

I looked at the code posted by theBanister and it works well. I then changed it from referencing a calendar control to a ComboBox and I had no problem. However, I do want to be able to trap the events of the combobox in a datagrid when a user activates the DropDown and the DropDownClosed events.  For example, if I dragged the ComboBox onto a Form, I can then write specific code for the named control's events. How do I do this when the control is hosted Thanks for helping...anyone Below is the modified code for a hosted combobox.

#region Using directives

using System;

using System.Collections.Generic;

using System.Text;

using System.Windows.Forms;

public class ComboBoxColumn : DataGridViewColumn

public ComboBoxColumn()

: base(new ComboBoxCell())

public override DataGridViewCell CellTemplate

get

return base.CellTemplate;

set

// Ensure that the cell used for the template is a ComboBoxCell.

if (value != null && !value.GetType().IsAssignableFrom(typeof(ComboBoxCell)))

throw new InvalidCastException("Must be a ComboBoxCell");

base.CellTemplate = value;

public class ComboBoxCell : DataGridViewTextBoxCell

public ComboBoxCell()

: base()

// Use the short date format.

// this.Style.Format = "d";

public override void InitializeEditingControl(int rowIndex, object initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)

// Set the value of the editing control to the current cell value.

base.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle);

ComboBoxEditingControl ctl = DataGridView.EditingControl as ComboBoxEditingControl;

// ctl.Text = this.Value.ToString();

public override Type EditType

get

// Return the type of the editing contol that ComboBoxCell uses.

return typeof(ComboBoxEditingControl);

public override Type ValueType

get

// Return the type of the value that ComboBoxCell contains.

return typeof(string);// DateTime);

public override object DefaultNewRowValue

get

// Use the current date and time as the default value.

return ""; // DateTime.Now;

public class ComboBoxEditingControl : ComboBox, IDataGridViewEditingControl

protected int rowIndex;

protected DataGridView dataGridView;

protected bool valueChanged = false;

public ComboBoxEditingControl()

protected override void OnTextChanged(EventArgs e)

base.OnTextChanged(e);

// Let the DataGridView know about the value change

// Notify DataGridView that the value has changed.

protected virtual void NotifyDataGridViewOfValueChange()

this.valueChanged = true;

if (this.dataGridView != null)

this.dataGridView.NotifyCurrentCellDirty(true);

#region IDataGridViewEditingControl Members

// Indicates the cursor that should be shown when the user hovers their

// mouse over this cell when the editing control is shown.

public Cursor EditingPanelCursor

get

return Cursors.IBeam;

public Cursor EditingControlCursor

get

return base.Cursor;

// Returns or sets the parent DataGridView.

public DataGridView EditingControlDataGridView

get

return this.dataGridView;

set

this.dataGridView = value;

// Sets/Gets the formatted value contents of this cell.

public object EditingControlFormattedValue

set

this.Text = value.ToString();

get

return this.Text;

// Get the value of the editing control for formatting.

public object GetEditingControlFormattedValue(DataGridViewDataErrorContexts context)

return this.Text;

// Process input key and determine if the key should be used for the editing control

// or allowed to be processed by the grid. Handle cursor movement keys for the ComboBox

// control; otherwise if the DataGridView doesn't want the input key then let the editing control handle it.

public bool EditingControlWantsInputKey(Keys keyData, bool dataGridViewWantsInputKey)

switch (keyData & Keys.KeyCode)

case Keys.Right:

//

// If the end of the selection is at the end of the string

// let the DataGridView treat the key message

//

if (!(this.SelectionLength == 0

&& this.SelectionStart == this.ToString().Length))

return true;

break;

case Keys.Left:

//

// If the end of the selection is at the begining of the

// string or if the entire text is selected send this character

// to the dataGridView; else process the key event.

//

if (!(this.SelectionLength == 0

&& this.SelectionStart == 0))

return true;

break;

case Keys.Home:

case Keys.End:

if (this.SelectionLength != this.ToString().Length)

return true;

break;

case Keys.Prior:

case Keys.Next:

if (this.valueChanged)

return true;

break;

case Keys.Delete:

if (this.SelectionLength > 0 || this.SelectionStart < this.ToString().Length)

return true;

break;

//

// defer to the DataGridView and see if it wants it.

//

return !dataGridViewWantsInputKey;

// Prepare the editing control for edit.

public void PrepareEditingControlForEdit(bool selectAll)

if (selectAll)

else

//

// Do not select all the text, but position the caret at the

// end of the text.

//

this.SelectionStart = this.ToString().Length;

// Indicates whether or not the parent DataGridView control should

// reposition the editing control every time value change is indicated.

// There is no need to do this for the ComboBox.

public bool RepositionEditingControlOnValueChange

get

return false;

// Indicates the row index of this cell. This is often -1 for the

// template cell, but for other cells, might actually have a value

// greater than or equal to zero.

public int EditingControlRowIndex

get

return this.rowIndex;

set

this.rowIndex = value;

// Make the ComboBox control match the style and colors of

// the host DataGridView control and other editing controls

// before showing the editing control.

public void ApplyCellStyleToEditingControl(DataGridViewCellStyle dataGridViewCellStyle)

this.Font = dataGridViewCellStyle.Font;

this.ForeColor = dataGridViewCellStyle.ForeColor;

this.BackColor = dataGridViewCellStyle.BackColor;

// this.TextAlign = translateAlignment(dataGridViewCellStyle.Alignment);

// Gets or sets our flag indicating whether the value has changed.

public bool EditingControlValueChanged

get

return valueChanged;

set

this.valueChanged = value;

#endregion // IDataGridViewEditingControl.

/// Routine to translate between DataGridView

/// content alignments and text box horizontal alignments.

private static HorizontalAlignment translateAlignment(DataGridViewContentAlignment align)

switch (align)

case DataGridViewContentAlignment.TopLeft:

case DataGridViewContentAlignment.MiddleLeft:

case DataGridViewContentAlignment.BottomLeft:

return HorizontalAlignment.Left;

case DataGridViewContentAlignment.TopCenter:

case DataGridViewContentAlignment.MiddleCenter:

case DataGridViewContentAlignment.BottomCenter:

return HorizontalAlignment.Center;

case DataGridViewContentAlignment.TopRight:

case DataGridViewContentAl

ignment.MiddleRight:

case DataGridViewContentAlignment.BottomRight:

return HorizontalAlignment.Right;

throw new ArgumentException("Error: Invalid Content Alignment!");

There is already a DataGridViewComboBoxColumn; you don't need to create your own to handle the editing-control events. To add handlers to editing-control events, you must do it in an EditingControlShowing event handler:

private void dataGridView1_EditingControlShowing(object sender,
  DataGridViewEditingControlShowingEventArgs e)
{
  ComboBox combo = e.Control as ComboBox;
  if (combo != null)
  {
    // Remove an existing event-handler, if present, to avoid 
    // adding multiple handlers when the editing control is reused.
    combo.SelectedIndexChanged -=
      new EventHandler(ComboBox_SelectedIndexChanged);

    // Add the event handler. 
    combo.SelectedIndexChanged +=
      new EventHandler(ComboBox_SelectedIndexChanged);
  }
}

Regards,

Glen

Hi Timothy,

If you are still having your issue, the first thing to check is that the KeyDown event is occurring for your editing control. If it is not, then make sure your EditingControlWantsInputKey implementation is returning true for the keys you are interested in. If this does not resolve your issue, then please post a brief repro snippet.

Hi CDFITGUY,

I don't think the Clone issue is related to this issue. You should be able to add rows programmatically like this:

this.dataGridView1.Rows.Add(new object[] { DateTime.Now });
this.dataGridView1.Rows.Add(new object[] { new DateTime(1999, 12, 31)});

The Clone issue is just that when you override an existing type with a Clone method (typically a cell or column type) and you add new properties, you must be sure to override Clone so that the new properties get copied along with everything else. This is necessary because the DataGridView architecture uses the Clone method in various ways behind the scenes, and any properties you add to a type will not get copied if you do not override Clone. The CalendarColumn type does not add any properties, so you don't need to override Clone. For an example of an overridden Clone method, see the DataGridViewDisableButton type in How to: Disable Buttons in a Button Column in the Windows Forms DataGridView Control.

The Rows collection has two Add method overloads that let you populate the values. You can either create a DataGridViewRow, populate it however you want, and pass it to the Add method, or you can pass in an object array where each value in the array corresponds to a column.

If you create a new DataGridViewRow, you can set the values for specific cells like the calendar cells and ignore the rest, which will get their values from their DefaultNewRowValue properties.

DataGridViewRow row = new DataGridViewRow();
row.Cells["DueDate"].Value = new DateTime(2006,6,23);
row.Cells["OrderDate"].Value = new DateTime(2006,6,10);
this.dataGridView1.Rows.Add(row);

If you pass an object array to the Add method instead, you have to provide values in the same order as the columns. You pass an object array in this case because each column might have a different value type.

this.dataGridView1.Rows.Add(new object[] {
new DateTime(2006, 6, 23),
"Urgent",
57.34f,
null,
new DateTime(2006,6,10)
});

If you pass in too many values, the extra values are ignored, and the Add method returns false. If you pass in too few values, the remaining cells will get their DefaultNewRowValue property values. This overload is not very convenient if you want to set default values for later columns but you want earlier columns to keep their DefaultNewRowValue values.

When you pass an object array to the Add method, it creates a new row by cloning the DataGridView.RowTemplate row. If you have set the RowTemplate property, but want to use the Add overload that takes a row, you should create your initial row by cloning the RowTemplate yourself.