DataGrid as supplied supports two column types:
DataGridTextBoxColumn for editing Strings and
DataGridBoolColumn for editing Booleans.
Of course, the Windows Forms Library developers realized that this would not be sufficient, so they provided a base class (
DataGridColumnStyle) that can be used to implement additional column types. This article discusses the enhancement of the
DataGrid with new column types to allow the editing of a wide range of data types. The source for these enhancements is released to the public domain as part of the
The screen grab above shows a simple demonstration application that allows the input of the contributors for a set of scientific fields. The
DataSet schema is shown below. Each contributor has a photo column and a number of property columns for dates of birth and death and colour code.
To keep the sample simple, the data is persisted by writing the
DataSet to disk as an
XmlDocument. In a real application,
DataSet changes would of course be persisted to a Data Tier - probably a database such as Microsoft SQL Server.
New Column Styles
For this demo, we'll be augmenting the column types with:
DataGridDataPictureColumn for editing Pictures and
DataGridPropertyEditorColumn for editing pretty well any other data type.
Because the AgileStudio product from which this code is derived is an add-in for Visual Studio, it is able to override the standard collection editor for
ColumnStyles. Thus, the Add dropdown lists all the column styles available. Indeed, the designer is also overridden to allow columns to be added to a
DataGrid with Drag and Drop.
Because the demo in this article is standalone, you will only see the two standard column styles in your editor and will have to manually add the appropriate code. (One way to do this is to add a standard
DataGridTextBoxColumn and then change its type afterwards in the code window. Once you have done this, you will be able to change properties such as
Mapping in the editor.) If you are interested in how to avoid this, let me know and I'll cover it in a subsequent article.
Friend WithEvents DataGridPropertyEditorColumn1 As _
Me.DataGridPropertyEditorColumn1 = _
<System.Diagnostics.DebuggerStepThrough()> Private Sub _
Me.DataGridPropertyEditorColumn1.HeaderText = "Born"
Me.DataGridPropertyEditorColumn1.MappingName = "Born"
Me.DataGridPropertyEditorColumn1.NullText = ""
Me.DataGridPropertyEditorColumn1.PropertyType = GetType(System.DateTime)
Me.DataGridPropertyEditorColumn1.UseStringAsUnderlyingType = False
Me.DataGridPropertyEditorColumn1.Width = 150
This is done by having a column of type
DataGridDataPictureColumn. A right mouse click will bring up a context menu to allow the transfer of images via the clipboard or to allow the pasting of an image from a file.
Currently, ADO.NET only supports a small range of data types. For this reason, the picture field is encoded as
base64Binary which is equivalent in .NET types to an array of
byte. Internal functions
ImageToByteArray handle the required conversions.
If you are using Microsoft SQL Server as your data tier, make sure you are handling base64 binary correctly. For example, if you are getting the data as XML, use a statement like the following:
SELECT ... FOR XML EXPLICIT,BINARY BASE64
Editing nearly any other Data Type
This is accomplished by having a column of type
DataGridPropertyEditorColumns in this example makes use of two editors - one for
System.DateTime and one for
System.Drawing.Color. Both these were implemented by Microsoft as DropDowns. This is the most common method, but editors for some types, for example,
System.Drawing.Font, are implemented as Popup Dialogs.
The really nice thing is that there are dozens of
TypeConverters included with .NET as standard. These are needed to drive the
PropertyGrid that is used to edit properties in Visual Studio. You get to leverage all this functionality with almost no work. Just set the
PropertyType property in your column as appropriate and everything else is automatic. It is also fairly easy to implement a
UITypeEditor for a type that you have written yourself.
There is one other property of
DataGridPropertyEditorColumn that is important to mention:
UseStringAsUnderlyingType. This should be set to
true when binding to a
DataSet if the type that you are binding is not one of the types supported by
DataSet (For example,
System.DateTime is supported, but
System.Drawing.Color is not.) If you are binding to a different data source that does not have this restriction, you can always set
false for more efficient data transfer.
Points of Interest
PropertyEditor internally to handle a cell in edit mode. Both these controls can be used independently outside the
DataGrid using standard simple data binding.
The source code for the
SekosPD.Windows.Forms library is released to the public domain and is available here. Reference style documentation for the library source will be available here. You may also want to read the article "Edit Almost Anything - Part I", which examines other controls as well as the
The code released with this article is based on a portion of the AgileStudio product, which extends Visual Studio. Check out the free evaluation here which automatically maintains the datasets and SQL StoreProcs required for a specific user interface (for Windows or Web applications).
The code in this article is currently in VB.NET. If you would like a version in C#, let me know. I would also like to examine some of the really neat things that you can do with
CollectionEditors to make the
DataGridPropertyEditorColumn really fly. If you would like an article about this, get in touch.