Express Yourself with Expression-based Columns Sample 1
Imports System.Data
Imports System.Data.SqlClient
Public Class Form1
Inherits System.Windows.Forms.Form
#Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'This call is required by the Windows Form Designer.
InitializeComponent()
'Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents gridCustOrders As System.Windows.Forms.DataGrid
Friend WithEvents cboYears As System.Windows.Forms.ComboBox
Friend WithEvents cboEmployees As System.Windows.Forms.ComboBox
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
Me.gridCustOrders = New System.Windows.Forms.DataGrid()
Me.cboYears = New System.Windows.Forms.ComboBox()
Me.cboEmployees = New System.Windows.Forms.ComboBox()
CType(Me.gridCustOrders, System.ComponentModel.ISupportInitialize).BeginInit()
Me.SuspendLayout()
'
'gridCustOrders
'
Me.gridCustOrders.DataMember = ""
Me.gridCustOrders.HeaderForeColor = System.Drawing.SystemColors.ControlText
Me.gridCustOrders.Location = New System.Drawing.Point(8, 40)
Me.gridCustOrders.Name = "gridCustOrders"
Me.gridCustOrders.Size = New System.Drawing.Size(672, 256)
Me.gridCustOrders.TabIndex = 1
'
'cboYears
'
Me.cboYears.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList
Me.cboYears.Location = New System.Drawing.Point(8, 8)
Me.cboYears.Name = "cboYears"
Me.cboYears.Size = New System.Drawing.Size(152, 21)
Me.cboYears.TabIndex = 2
'
'cboEmployees
'
Me.cboEmployees.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList
Me.cboEmployees.Location = New System.Drawing.Point(352, 8)
Me.cboEmployees.Name = "cboEmployees"
Me.cboEmployees.Size = New System.Drawing.Size(328, 21)
Me.cboEmployees.TabIndex = 3
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(688, 301)
Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.cboEmployees, Me.cboYears, Me.gridCustOrders})
Me.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedDialog
Me.MaximizeBox = False
Me.Name = "Form1"
Me.Text = "Computed columns..."
CType(Me.gridCustOrders, System.ComponentModel.ISupportInitialize).EndInit()
Me.ResumeLayout(False)
End Sub
#End Region
Public data As DataSet
Private m_CmdYears As String = "SELECT DISTINCT year(orderdate) AS Year FROM orders"
Private m_CmdCustomers As String = "SELECT customerid, companyname, city FROM customers"
Private m_CmdEmployees As String = "SELECT * FROM employees"
Private m_CmdOrders As String = "SELECT o.customerid, od.orderid, o.employeeid, o.orderdate, SUM(quantity*unitprice) AS price FROM Orders o , [Order Details] od WHERE o.orderid=od.orderid GROUP BY o.customerid, od.orderid, o.employeeid, o.orderdate"
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
End Sub
Public Sub ColumnChanged(ByVal sender As Object, ByVal e As DataColumnChangeEventArgs)
MsgBox(e.Column.ColumnName + " changed!")
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
LoadData()
End Sub
Private Sub LoadData()
' establish the connection
Dim conn As SqlConnection = New SqlConnection("DATABASE=northwind;SERVER=localhost;Integrated Security=SSPI;")
Dim da As SqlDataAdapter
data = New DataSet()
' load years
da = New SqlDataAdapter(m_CmdYears, conn)
da.Fill(data, "Years")
' load customers
da = New SqlDataAdapter(m_CmdCustomers, conn)
da.Fill(data, "Customers")
' load employees
da = New SqlDataAdapter(m_CmdEmployees, conn)
da.Fill(data, "Employees")
Dim dt As DataTable = data.Tables("Employees")
dt.Columns.Add("EmployeeName", GetType(String), "lastname + ', ' + firstname")
' load orders
da = New SqlDataAdapter(m_CmdOrders, conn)
da.Fill(data, "Orders")
' set relations
Dim rel As DataRelation
rel = New DataRelation("CustToOrders", _
data.Tables("Customers").Columns("customerid"), _
data.Tables("Orders").Columns("customerid"))
data.Relations.Add(rel)
data.Tables("Customers").Columns.Add("Total", GetType(Decimal), "sum(child(CustToOrders).price)")
' Save to XML
data.WriteXml("data.xml", XmlWriteMode.WriteSchema)
' data binding
cboYears.DataSource = data.Tables("Years")
cboYears.DisplayMember = "Year"
cboEmployees.DataSource = data.Tables("Employees")
cboEmployees.DisplayMember = "EmployeeName"
gridCustOrders.DataSource = data
gridCustOrders.DataMember = "Customers"
End Sub
End Class