|By Bruce Armstrong||
|September 3, 2005 12:00 PM EDT||
Last month we saw how DataWindow.NET technology can be a benefit when used for data presentation and data access in a Windows Forms (WinForms) application. This month we're going to look at how DataWindow.NET technology is a simpler but more powerful way of formatting data in the presentation layer.
Once again, we'll be taking a sample application provided by Microsoft for .NET and implementing it using DataWindow.NET technology. In this case, we're using the Visual Basic .NET Code Sample: DataGrid Formatting sample application available at www.microsoft.com/downloads/details.aspx? FamilyID=28fd458f-5571-42b4-a2fe-09b69ddf0863&displaylang=en.
As with last month's article, the original sample was written to connect to the Microsoft Northwind sample database. So you'll need MSDE or SQL Server with that sample database installed if you want to try it out for yourself. Also like last month's article, the sample code for this article is intended as an addition to the original sample so you can compare them side-by-side. After adding the sample code files from this article to the original sample, you can switch between the DataGrid and DataWindow implementations by changing the startup form for the project (see Figure 1).
The main form of the application consists of a DataGrid or DataWindow and four command buttons that apply "Default," "Table Style," "Column Style," and "Grid Properties" formatting to the DataGrid or DataWindow control. Table 1 shows the results of the different formatting applied to the DataGrid and DataWindow respectively.
The primary difference between the DataGrid and DataWindow implementations with regard to form variables is that the DataGrid has a DataSet defined (ProductData) and a constant (PRODUCT_TABLE_NAME). This particular VB.NET example, unlike the last two we looked at, is a typical ADO.NET sample that uses a DataAdapter and a DataSet to retrieve and store the data and then fill the DataGrid. The PRODUCT_TABLE_NAME constant is used to name the result set of interest in the DataSet because a .NET DataSet can actually hold multiple result sets.
Each of the command buttons calls two form methods (ResetDemo and BindDataGrid or BindDataWindow) and then a third form method for the non-default styles that sets up that particular style (see Table 2).
In the DataGrid implementation, the ResetDemo method clears the DataSet and then resets each of the various formatting properties that get set during the demo.
If Not IsNothing(ProductData.Tables(PRODUCT_TABLE_NAME)) Then
.BackgroundColor = SystemColors.InactiveCaptionText
.CaptionText = ""
.CaptionBackColor = SystemColors.ActiveCaption
.BorderStyle = DefaultGridBorderStyle
The DataWindow implementation of ResetDemo is much simpler because we only need to reset the properties on the DataWindow control. The properties of the DataWindow object get reset during the BindDataWindow method when we reassign the DataWindow object to the control.
dw_products.BorderStyle = DataWindowBorderStyle.None
dw_products.TitleBar = False
dw_products.Text = ""
Both the BindDataGrid and BindDataWindow methods try to connect to the SQL Server version of the Northwind database and then try to connect to the MSDE version if the SQL Server version can't be found. The DataGrid implementation then uses an SqlDataAdapter class to retrieve the data from the database and routes it to the DataSet. Then it assigns that DataSet as the DataSource for the DataGrid control.
Dim ProductAdapter As New SqlDataAdapter( _
"SELECT ProductID, ProductName, UnitPrice, UnitsInStock FROM products", _
grdProducts.DataSource = ProductData.Tables(PRODUCT_TABLE_NAME)
The DataWindow implementation of the BindDataWindow method does pretty much the same thing using DataWindow related classes. First the OleDB connection is bound to a DataWindow.AdoTransaction object. We then reset the DataWindow object assigned to the DataWindow control, assign the AdoTransaction object to the DataWindow control, and then retrieve the DataWindow.
Dim SQLCA As New Sybase.DataWindow.AdoTransaction(conn, "")
dw_products.LibraryList = "dwgridformatting.pbl"
dw_products.DataWindowObject = ""
dw_products.DataWindowObject = "d_g_products"
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