Hola:
EJEMPLO1
Un Form con 1 boton (btnColumnaCalculada) y 1 DataGridView (DataGridView1)
Pegar el siguiente codigo.
Imports System.Data.SqlClient
Public Class Form1
Inherits System.Windows.Forms.Form
Private oConnection As SqlConnection
Private oDataAdapter As SqlDataAdapter
Private oDataSet As DataSet
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
' carga inicial del dataset y datagrid
oConnection = New SqlConnection("Data Source=.\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True")
oDataAdapter = New SqlDataAdapter("SELECT OrderID,CustomerID,Freight FROM Orders", oConnection)
oDataSet = New DataSet
oConnection.Open()
oDataAdapter.Fill(oDataSet, "Orders")
oConnection.Close()
Me.DataGridView1.DataSource = oDataSet
Me.DataGridView1.DataMember = "Orders"
End Sub
Private Sub btnColumnaCalculada_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnColumnaCalculada.Click
' al pulsar un botón, recuperamos del dataset asignado al datagrid
' un objeto dataview al que le añadimos una columna calculada,
' finalmente añadimos el dataview al datagrid
Me.DataGridView1.DataSource = Nothing
Dim colNueva As DataColumn = New DataColumn("ValorDoble")
colNueva.Expression = "Freight * 2"
Dim dvVistaDatos As DataView = oDataSet.Tables("Orders").DefaultView
dvVistaDatos.Table.Columns.Add(colNueva)
Me.DataGridView1.DataSource = dvVistaDatos
Me.btnColumnaCalculada.Enabled = False
End Sub
End Class
EJEMPLO2
Un Form con 1 DataGridView (DataGridView1)
Pegar el siguiente codigo.
Imports System.Data.SqlClient
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim cnConexion As SqlConnection = New SqlConnection()
cnConexion.ConnectionString = "Data Source=.\SQLEXPRESS;Initial Catalog=AdventureWorks;Integrated Security=True"
Dim sSQL As String
sSQL = "select ProductID,StandardPrice,LastReceiptCost,(LastReceiptCost-StandardPrice) as Diferencia "
sSQL &= "from Purchasing.ProductVendor"
Dim cmdComando As SqlCommand = New SqlCommand(sSQL, cnConexion)
Dim daAdaptador As SqlDataAdapter = New SqlDataAdapter(cmdComando)
Dim dsDatos As DataSet = New DataSet()
daAdaptador.Fill(dsDatos, "ProductVendor")
Me.DataGridView1.DataSource = dsDatos
Me.DataGridView1.DataMember = "ProductVendor"
Dim DobleDiferencia As DataGridViewTextBoxColumn = New DataGridViewTextBoxColumn()
DobleDiferencia.HeaderText = "Doble Diferencia precios"
DobleDiferencia.Name = "Doble Diferencia"
Me.DataGridView1.Columns.Add(DobleDiferencia)
End Sub
Private Sub DataGridView1_CellFormatting(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) Handles DataGridView1.CellFormatting
If Me.DataGridView1.Columns(e.ColumnIndex).Name = "Doble Diferencia" Then
Dim ldDiferencia As Double = CDbl(Me.DataGridView1.Rows(e.RowIndex).Cells("Diferencia").Value)
e.Value = ldDiferencia * 2
End If
End Sub
End Class
Espero que te sirva
Un saludo desde Bilbo
Carlos
