The document discusses three different ways to perform CRUD (create, read, update, delete) operations on a database using ADO.NET in Visual Basic.NET. It includes code examples showing how to connect to a SQL Server database, retrieve data from a table into a DataSet, display the data in a DataGridView, and search or filter the data. The examples demonstrate using DataAdapters, DataSets, DataViews and SqlDataReaders to connect to the database and perform queries to retrieve and manipulate the data.

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PRIMERA FORMA EN ADO.NET
VISUAL.NET
Imports System.Data.SqlClient
Public Class Form1
Dim CN As New SqlConnection("data source= . ; database = Northwind ; integrated security = true")
Dim DS As New DataSet
Dim DA As SqlDataAdapter
Dim BUSCAR As Integer
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
MyBase.Load
DA = New SqlDataAdapter("select * from Employees", CN)
DS = New DataSet
DA.Fill(DS, "Employees")
Me.DataGridView1.DataSource = DS.Tables("Employees")
End Sub
Private Sub btnnuevo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnnuevo.Click
Me.txtbuscar.Enabled = True
Me.txtbuscar.Text = ""
End Sub

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Private Sub btnbuscar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnbuscar.Click
Dim objdataview As New DataView
Dim buscar As Integer
Me.DataGridView1.DataSource = Nothing
buscar = Me.txtbuscar.Text
objdataview.Table = DS.Tables("Employees")
objdataview.RowFilter = "employeeid= '" & buscar & "'"
If objdataview.Count > 0 Then
Me.DataGridView1.DataSource = objdataview
Me.DataGridView1.Refresh()
Else
MsgBox("registro no encontrado", MsgBoxStyle.Information, "advertencia")
End If
Me.txtbuscar.Enabled = False
End Sub
End Class

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SEGUNDA FORMA EN ADO.NET
VISUAL BASIC.NET
USE MASTER
CREATE TABLE EMPLEADOS
(CODIGO NVARCHAR(5),
NOMBRE NVARCHAR(25),
APELLIDOS NVARCHAR (25),
DIRECCION NVARCHAR (25),
TELEFONO NVARCHAR (25))
INSERT INTO EMPLEADOS
VALUES ('E0001', 'RICHARD', 'RAMOS BARRIOS' , 'LA VISTORIA', '997798005')
INSERT INTO EMPLEADOS
VALUES ('E0002', 'JUAN ', 'CARLOS ROJAS' , 'MOLINA', '997798008')
INSERT INTO EMPLEADOS
VALUES ('E0003', 'CARLOS', 'LOLO CARLOS' , 'COMAS', '997798007')
INSERT INTO EMPLEADOS
VALUES ('E0004', 'NILDA', 'DURAND MORILLO' , 'LIMA', '997798009')
Imports System.Data.SqlClient
Public Class Form1
Dim CN As New SqlConnection("data source= . ;user id = 123 ; database = master ; integrated security
= true")

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Dim DS As New DataSet
Dim DA As SqlDataAdapter
Dim dW As New DataView
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
MyBase.Load
DA = New SqlDataAdapter("SELECT * FROM EMPLEADOS", CN)
DS = New DataSet
DA.Fill(DS, "EMPLEADOS")
Me.DataGridView1.DataSource = DS.Tables("EMPLEADOS")
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnnuevo.Click
Dim ctr As Control
For Each ctr In Me.Controls
If TypeOf ctr Is TextBox Then ctr.Text = ""
'Me.DataGridView1.DataSource = Nothing
Next
End Sub
Private Sub btnbuscar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnbuscar.Click
Me.DataGridView1.DataSource = Nothing
dW.Table = DS.Tables("empleados")
dW.RowFilter = "codigo = '" & txtcodigo.Text & "'"
If dW.Count > 0 Then
Me.DataGridView1.DataSource = dW
Me.DataGridView1.Refresh()
Me.txtcodigo.Text = Me.DataGridView1.Item(0, 0).Value
Me.txtnombre.Text = Me.DataGridView1.Item(1, 0).Value
Me.txtapellidos.Text = Me.DataGridView1.Item(2, 0).Value
Me.txtdireccion.Text = Me.DataGridView1.Item(3, 0).Value
Me.txttelefono.Text = Me.DataGridView1.Item(4, 0).Value
Else
MsgBox("REGISTRO NO ENCONTRADO")
End If
End Sub
End Class

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TERCERA FORMA ADO.NET
VISUAL BASIC.NET
USE MASTER
CREATE TABLE EMPLEADOS
(CODIGO NVARCHAR(5),
NOMBRE NVARCHAR(25),
APELLIDOS NVARCHAR (25),
DIRECCION NVARCHAR (25),
TELEFONO NVARCHAR (25))
INSERT INTO EMPLEADOS VALUES ('E0001', 'RICHARD' , 'RAMOS BARRIOS' , 'LA VISTORIA',
'997798005')
INSERT INTO EMPLEADOS VALUES ('E0002', 'JUAN ' , 'CARLOS ROJAS' , 'MOLINA', '997798008')
INSERT INTO EMPLEADOS VALUES ('E0003', 'CARLOS ' , 'LOLO CARLOS' , 'COMAS', '997798007')
INSERT INTO EMPLEADOS VALUES ('E0004', 'NILDA' , 'DURAND MORILLO' , 'LIMA', '997798009')
select * from empleados

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Imports System.Data.SqlClient
Public Class form1
Dim CN As New SqlConnection("data source= . ; database = MASTER; integrated security = true")
Dim cmd As SqlCommand
Dim dr As SqlDataReader
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnsalir.Click
End
End Sub
Private Sub btnnuevo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnnuevo.Click
Dim ctrl As Control
For Each ctrl In Me.Controls
If TypeOf ctrl Is TextBox Then ctrl.Text = ""
Next
Me.btnnuevo.Text = "buscar"
End Sub
Private Sub btnbuscar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
btnbuscar.Click
Try
If btnbuscar.Text = "buscar" Then
Me.btnbuscar.Text = "buscar ahora"
Me.txtcodigo.Enabled = True
Me.txtcodigo.Focus()
Else
cmd = New SqlCommand("select * from empleados where codigo = '" & Me.txtcodigo.Text & "'", CN)
CN.Open()
dr = cmd.ExecuteReader
If dr.Read Then
Me.txtnombre.Text = dr("nombre")
Me.txtapellidos.Text = dr("apellidos")
Me.txtdireccion.Text = dr("direccion")
Me.txttelefono.Text = dr("telefono")
Else
MessageBox.Show("el codigo no existe", "error", MessageBoxButtons.OK,
MessageBoxIcon.Information)
End If
CN.Close()
End If
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Sub
End Class

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