Article 2 - Display data using DataSet and DataGrid controls through Whidbey (VB.NET)

Introduction

My previous article explains about the step by step dynamic creation of a SQL Server database, tables, and stored procedure using Visual Studio codename Whidbey and VB.NET. I hope that you got a good start up in dynamic creation of SQL Server database and tables. This article explains how we can display data using DataSet and DataGrid controls after the database is created.

About �DataTable� and �DataSet� Objects

A DataSet is a major component of ADO.NET architecture. It is a set of data grouped together, which is an in-memory cache of data retrieved from a data source. A DataSet consists of a collection DataTable objects. A DataTable represents one table of in-memory data. The name of the DataTable is conditionally case-sensitive only if you set the public property of �CaseSensitive�, which indicates whether string comparisons within the table are case-sensitive.

For example, if you named a DataTable as �MyTable� and if you defined the table as �Mytable�, it won�t look for the table because DataTable name is case sensitive. DataSet and DataView are the two data objects that use the DataTable.

Some of the public properties of DataTable are shown below:

Properties Description

• CaseSensitive

  This property returns a Boolean value which checks if the table name is case-sensitive. It returns True if the comparison is case-sensitive; otherwise, False. For example, if you named a DataTable as �MyTable� and if you defined the table as �Mytable�, it won�t look for the table.

  The CaseSensitive property affects string comparisons in sorting, searching, and filtering.

• ChildRelations

  Simply, it is the relationship between two tables. It is just like database relationship keys such as primary key, secondary key etc., which will relate two tables using a key field.

• Columns

  Database fields or tuples.

• Constraints

  Constraints maintained for relationship between tables using keys such as primary key, index etc.

• DataSet

  Retrieves a set of data or records based on your table name.

• DefaultView

  Customized view of the table such as filtered view, or a cursor position.

• HasErrors

  If any row has errors, display errors.

• Locale

  Local information to compare the strings.

• MinimumCapacity

  Initial size of the table.

• ParentRelations

  Any relationship occuring with parent table.

• PrimaryKey

  A key used for unique identification of a row.

• Rows

  Number of rows as collections.

• TableName

  Name of the database table.

Some of the public methods of a DataTable are shown below:

• AcceptChanges

  Commits a transaction.

• BeginInit

  Initialization of DataTable.

• BeginLoadData

  Turns off notifications, index maintenance, and constraints.

• Clear

  Clears all the records from DataTable.

• Clone

  Copy the structure to another table (including constraints, key fields, schemas etc.).

• Compute

  Filter data based on expression.

• Copy

  Copies the database structure and data (not like Clone).

• Dispose

  Release from memory (unload).

• EndInit

  Fires when initialization ends.

• EndLoadData

  Fires when load data from DataTable ends.

• GetErrors

  Gets an array of DataRow objects that contain errors.

• ImportRow

  Importing records.

• LoadDataRow

  Updates the rows based on the condition. If no matching records found, it will insert the records.

• NewRow

  Creates a new row in DataTable.

• RejectChanges

  Rolls back the changes.

• Reset

  Reset the DataTable in original position.

• Select

  Gets an array of data records.

Some of the events associated with DataTable are ColumnChanged, ColumnChanging, RowChanged, RowChanging, RowDeleted, RowDeleting etc.

Note: System.Data namespace is used for including into your project, which consists mostly of the classes that constitute the ADO.NET architecture. The assembly name used for creating the DataSet object is System.Data in System.Data.dll file.

About �SQLDataAdapter� Class

SQLDataAdapter class is used to retrieve and update the database records in a DataSet. It is a bridge between SQL Server and DataSet.

There are two methods used for adding or updating records. They are:

• Add method which will fill or refresh the rows or records in a DataSet.
• Update method used for updating the records in a DataSet. Please note that this will call the respective SQL statements such as INSERT, UPDATE, or DELETE based on the SqlAdapter state.

The following lines of code will help you to understand how the SqlDataAdapter is responsible for using a SqlCommand object to fill a DataSet.

' fill a DataSet.

' A SqlCommand object is used to execute sql statements,

' which we already discussed the Article 1

Dim Mycmd As New SqlCommand(�SELECT * FROM dbo.Customer�, myConnection)
Dim mySqlDataAdapter As New SqlDataAdapter(Mycmd)
Dim mydsCustomer As New DataSet()
         
mySqlDataAdapter.Fill(mydsCustomer, "Customer")

About DataGrid Control

A DataGrid control fills the rows from a data source in a table. It is used to retrieve and update the database records. The DataGrid control supports selection, editing, deleting, paging, and sorting.

Different column types in a DataGrid determine the behavior of the columns in the control. Some of the column types are BoundColumn, ButtonColumn, EditCommandColumn, HyperLinkColumn, and TemplateColumn etc.

Note: System.Web.UI.WebControls namespace is used for including this object into your application. The assembly name used for creating the DataGrid control is System.Web in System.Web.dll file.

Steps to use the DataGrid control on your .NET form

A DataGrid control allows you to select, sort and edit the items from a data source in a table.

1. Bind a DataGrid to the DataSet.

   First, you need to bind the DataSet into a DataGrid, then set the Visible property to True. If you don�t set the Visible property to True, the DataGrid will still appear, but the scroll bar will be missing.

   ' Set the DataGrid caption, bind it to the DataSet, and then make it
   
   ' Visible            
   
   mydgCustomer.CaptionText = "Customer"
   ' Notice here that instead of using the DataSet table name, 
   
   ' "customers", the alternate syntax of table index is used.
   
   mydgCustomer.DataSource = mySqlDataAdapter.Tables(0)
   mydgCustomer.Visible = True

   Notice the syntax mySqlDataAdapter.Tables(0), you can also use the alternate syntax using the DataSet table name �Customer�.

2. Custom formatting a DataGrid.

   Table style object allows you to custom format the DataGrid object. The object name for custom formatting a DataGrid object is called DataGridTableStyle. It represents the table drawn by the System.Windows.Forms.DataGrid control at run time. It is a class file that represents applying custom formatting to draw the grid.

   The following is the list of DataGridTableStyle properties that can be set to override System.Windows.Forms.DataGrid control properties. This way, it allows your own custom formatting.

   • AllowSorting property allows you to set the sorting based on the user clicks on each column header, which will sort either in ascending or descending order. When the AllowSorting property is set to True, a triangle appears in each column header indicating the direction of the sort. The user can click on any column header to sort the grid by that column. Clicking the column a second time changes the direction of the sort. It returns True if sorting is allowed, otherwise, it returns False. The default value of this property is True.
   • AlternatingBackColor allows you to set the alternate row colors (or gets or sets the background color of odd-numbered rows of the grid).

     mydgCustomer.AlternatingBackColor = System.Drawing.Color.Red

   • BackColor property sets the background color of the object.
   • ColumnHeadersVisible property allows you to hide or make visible the column headers in a DataGrid control on your form.
   • ForeColor allows you set the foreground color of your DataGrid control.
   • GridLineColor allows you set the DataGrid line color.
   • GridLineStyle allows you to set the style of DataGrid.

     mydgCustomer.GridLineStyle = 
            System.Windows.Forms.DataGridLineStyle.None
     mydgCustomer.GridLineStyle = 
            System.Windows.Forms.DataGridLineStyle.Solid

   • HeaderBackColor allows you to set or get the background color of the headers.
   • HeaderFont allows you to set or get the header font on the DataGrid control.
   • HeaderForeColor sets the foreground color of the column headers.
   • LinkColor allows you to set the color of a web link text.
   • PreferredColumnWidth allows you to set the DataGrid column width.
   • PreferredRowHeight allows you to set the DataGrid row height.
   • ReadOnly property allows you to set the DataGrid to read only. No editing is possible (update, insert or delete).
   • RowHeadersVisible property allows you to get or set the visible properties of row headers on the DataGrid control.

Steps to display data using DataSet and DataGrid controls:

You understand now the basic functionality of DataTable and DataSet objects, DataAdapter classes, and DataGrid control. Next, I am going to explain the step by step creation of the usage of these objects or classes or controls in your .NET applications.

1. Creating and opening the database connection, database objects.

   If you want to learn more on creating the databases and tables, look at my previous article, which describes how to create and open a database connection using WhidBey or .NET environment. Also, the previous article explains how to open a SQL database connection if we only installed the MSDE. For solving this issue, we used SQL error exception code in .NET Whidbey.

2. Add the DataGrid control to your form.

   Add a new DataGrid control to your form, name it as mydgCustomer.

3. Bind to a DataGrid for display.

   After adding the DataGrid control on your form, next task is to populate data using DataAdapter. The following routine gets the customer information from the Mydatabase table, puts it into a DataSet which is used to bind to a DataGrid for display.

   If IsNothing(mydgCustomer.DataSource) Then
       Dim strMySQL As String = _
         "USE MyDatabase " & vbCrLf & _
         "SELECT * " & _
         "FROM myStoredProcedure"
       Try
           ' The SqlConnection class allows you to communicate
   
           ' with SQL Server and DataTable.
   
           Dim myConnection As New SqlConnection(myConnection) 
           ' A SqlCommand object is used to execute the SQL commands.
   
           Dim mycmd As New SqlCommand(strMySQL, myConnection) 
           Dim mySqlDataAdapter As New SqlDataAdapter(mycmd)
           Dim mydsCustomer As New DataSet() 
           ' The SqlDataAdapter is responsible for using
   
           ' a SqlCommand object to fill a DataSet. 
   
           mySqlDataAdapter.Fill(mydsCustomer, "Customer") 
           ' Set the DataGrid caption, bind it to the DataSet,
   
           ' and then make it Visible            
   
           mydgCustomer.CaptionText = "Customer" 
           ' Notice here that instead of using the DataSet table name, 
   
           ' "Customers", the alternate syntax of table index is used. 
   
           mydgCustomer.DataSource = mySqlDataAdapter.Tables(0) 
           ' Settings to the DataGrid Styles, which will call the procedure
   
           ' setMyDataGridTableStyleProperties and the parameter
   
           ' as DataGrid
   
           setMyDataGridTableStyleProperties(mydgCustomer)
           mydgCustomer.Visible = True
   
       Catch sqlExc As SqlException 
           MessageBox.Show(sqlExc.ToString, "SQL Exception Error!", _
                       MessageBoxButtons.OK, MessageBoxIcon.Error) 
       End Try 
   End If

4. Update the DataGrid style properties.

   The procedure setMyDataGridTableStyleProperties allows you to set the DataGrid style properties, passing the DataGrid as an object parameter.

   First, we need to create the DataGrid style using DataGridTableStyle object, and can apply the style properties such as AlternatingBackColor, BackColor, ForeColor, GridLineColor, HeaderrBackColor, HeaderFont, HeaderForeColor, LinkColor, Mapping, etc. AddRange method functionality allows you to set the styles in a particular range of your DataGrid component.

   Private Sub setMyDataGridTableStyleProperties (ByRef myDG as DataGrid)
   ' Use a table style object to apply custom formatting 
   
   ' to the  DataGrid.
   
   
       Dim mydgTableStyle As New DataGridTableStyle()
       Dim mygrdColStyle1, mygrdColStyle2, mygrdColStyle3, _
          mygrdColStyle4, mygrdColStyle5 As New   & _
          DataGridTextBoxColumn() 
       With mydgTableStyle
           .AlternatingBackColor = Color.LightCoral
           .BackColor = Color.LawnGreen
           .ForeColor = Color.LightGray
           .GridLineColor = Color.LightGreenrodYellow
           .GridLineStyle = System.Windows.Forms.DataGridLineStyle.
           .HeaderBackColor = Color. LightGray
           .HeaderFont = New Font("Courier", 10.0!, FontStyle.Bold)
           .HeaderForeColor = Color. LawnGreen
           .LinkColor = Color.Teal 
           ' Do not forget to set the MappingName property. 
   
           ' Without this, the DataGridTableStyle properties
   
           ' and any associated DataGridColumnStyle objects
   
           ' will have no effect. 
   
           .MappingName = "Customers" 
           .SelectionBackColor = Color. LawnGreen
           .SelectionForeColor = Color. LightGray
       End With 
       ' Use column style objects to apply formatting specific
   
       ' to each  column of customer table.
   
       With mygrdColStyle1
           .HeaderText = "ID#"
           .MappingName = "CustomerID"
           .Width = 50
       End With 
       With mygrdColStyle2
           .HeaderText = "Last Name"
           .MappingName = "NameLast"
           .Width = 140
       End With 
       With mygrdColStyle3
           .HeaderText = "Address"
           .MappingName = "Address1"
           .Width = 180
       End With 
       With mygrdColStyle4
           .HeaderText = "State"
           .MappingName = "State"
           .Width = 30
       End With 
       With mygrdColStyle5
           .HeaderText = "Phone"
           .MappingName = "Phone"
           .Width = 70
       End With
       ' Add the column style objects to the tables style's 
   
       ' column styles collection. If you fail to do this the column 
   
       '  styles will not apply.
   
       mydgTableStyle.GridColumnStyles.AddRange _
                       (New DataGridColumnStyle() _
                       { mygrdColStyle1, mygrdColStyle2, _
                       mygrdColStyle3, mygrdColStyle4, mygrdColStyle5})
       ' Add the table style object to the DataGrid's table styles 
   
       ' collection. Again, failure to add the style to the collection 
   
       ' will cause the style to not take effect.
   
   
       myDG.TableStyles.Add(mydgTableStyle)
   End Sub

Requirements

• Microsoft Visual Studio.Whidbey Ver 8.0 or
• Microsoft Visual Studio .NET Professional or greater.
• Windows 2000 or Windows XP.

Summary:

From this article, we found the description of DataSet, DataTable objects, DataAdapter classes. Also, you got a brief idea of using DataGrid using Fill method from the DataAdapter class. It also explained how to use the styles in DataGrid.

If you need any suggestions or help, contact me at benoyraj@yahoo.com.