Nullable datetime column in .NET DataGrid with DateTimePicker

• Download sources - 3.41 KB
• Download sample - 400 KB

Introduction

I have always known a lot of people who have problems with the standard .NET 2.0 DataGridView and the nullable DateTime column (created with Oracle PL/SQL column definition):

dtReceived DATE

or a MS SQL Server DateTime column with NULL values in Transact SQL:

dtReceived DATETIME NULL

Google Search normally gives this Microsoft sample for calendar columns: How to: Host Controls in Windows Forms DataGridView Cells. This is a good start point, but it isn't enough. You can never correctly fill DateTime DataGridView cells with NULL. I found many variants for the simple DateTimePicker class, but work samples absent for nullable DateTime columns in a DataGridView.

Solution

I spent a lot of time on the Internet searching, and found a nice article about a nullable DateTimePicker: DateTimePicker DBNull. I then made several corrections and as 'magic touch', and it works for DataGridViews now.

Using the code

These are the steps we need:

1. Rename the class DateTimePicker to DatePicker (the same name for different classes is a bad practice, in my opinion):

public class DatePicker : System.Windows.Forms.DateTimePicker
{..

2. Add the following code snippet to the DatePicker class:

public string ToShortDateString() 
{ 
    if (!realDate) 
        return String.Empty; 
    else 
    { 
        DateTime dt = (DateTime)Value; 
        return dt.ToShortDateString(); 
    }
}

3. Correct CalendarEditingControl.cs from the Microsoft Sample for usage in our DatePicker:

class CalendarEditingControl : DatePicker, IDataGridViewEditingControl { ...

4. Correct CalendarCell.cs from the Microsoft Sample for DBNull:

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;

    // ++ vic 14-aug-2009
     object val = null;
     try 
     {
          val = this.Value;
     }
     catch (Exception ex)
     { 
          // Argument ot of range (value doesn't exists in collection)
          return;
     }
     
     if (val != System.DBNull.Value)
          ctl.Value = (DateTime)val;
}

That's all, folks :)

You should press the DEL key to set a NULL filled DateTime cell.

The source code is attached. You can directly use the files from my project in your projects like in the Microsoft Samples (DatePicker.cs, CalendarCell.cs, CalendarColumn.cs, CalendarEditingControl.cs):

private void Form1_Load(object sender, EventArgs e)
{
     CalendarColumn col = new CalendarColumn();
     this.dataGridView1.Columns.Add(col);
     this.dataGridView1.RowCount = 5;
     foreach (DataGridViewRow row in this.dataGridView1.Rows)
     {
          row.Cells[0].Value = DateTime.Now;
     }
}

or from the Microsoft Visual Studio Data Designer for DataGrid (right mouse click on DataGridView, and choose 'Edit columns' from the context menu):

I have attached a real sample with database (Visual Studio 2008 / SQL Express database).

History

• 14-Aug-2009: Initial version posted.
• 16-Aug-2009: Database sample added.

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)