Introduction
Windows Forms 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 SekosPD.Windows.Forms
library.
Demo Application
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 _
SekosPD.Windows.Forms.DataGridPropertyEditorColumn
�
Me.DataGridPropertyEditorColumn1 = _
New SekosPD.Windows.Forms.DataGridPropertyEditorColumn
�
<System.Diagnostics.DebuggerStepThrough()> Private Sub _
InitializeComponent()
�
'
'DataGridPropertyEditorColumn1
'
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
Editing Pictures
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 ByteArrayToImage
and 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 DataGirdPropertyEditorColumn
. The 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 UITypeEditor
s and TypeConverter
s 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 TypeConverter
and 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 UseStringAsUnderlyingType
to false
for more efficient data transfer.
Points of Interest
DataGridDataPictureColumn
and DataGridPropertyEditorColumn
employ DataPicture
and 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 DataGrid
.
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).
Conclusion
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 UITypeEditor
s including CollectionEditor
s to make the DataGridPropertyEditorColumn
really fly. If you would like an article about this, get in touch.