Code sample demonstrating how to Select/Insert/Delete/Update records in SQL Server Compact database file(*.sdf) in VB.NET.

Imports System.Data.SqlServerCe

Public Class Form1

    ' Shared variables
    Dim con As SqlCeConnection = New SqlCeConnection("Data Source=C:\Northwind.sdf")
    Dim cmd As SqlCeCommand
    Dim myDA As SqlCeDataAdapter
    Dim myDataSet As DataSet

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ShowData()
    End Sub

    'Binding database table to DataGridView
    Public Sub ShowData()
        cmd = New SqlCeCommand("Select * FROM Users", con)
        If con.State = ConnectionState.Closed Then con.Open()
        myDA = New SqlCeDataAdapter(cmd)
        myDataSet = New DataSet()
        myDA.Fill(myDataSet, "MyTable")
        DataGridView1.DataSource = myDataSet.Tables("MyTable").DefaultView
    End Sub

    ' Retrieve/Select records  
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        cmd = New SqlCeCommand("SELECT * FROM Users Where name='Martin'", con)
        If con.State = ConnectionState.Closed Then con.Open()
        Dim sdr As SqlCeDataReader = cmd.ExecuteReader()
        While sdr.Read = True
            MessageBox.Show(sdr.Item("name") & " " & sdr.Item("phone"))
        End While
        sdr.Close()
    End Sub

    ' Insert record  
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        cmd = New SqlCeCommand("Insert Into Users(name, phone) Values('phenry', ‘88866677’)", con)
        If con.State = ConnectionState.Closed Then con.Open()
        cmd.ExecuteNonQuery()
        ShowData() 'Rebinding to DataGridView and view result
    End Sub

    ' Update record
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        cmd = New SqlCeCommand("Update Users Set phone=’34’ Where name='Martin'", con)
        If con.State = ConnectionState.Closed Then con.Open()
        cmd.ExecuteNonQuery()
        ShowData() 'Rebinding to DataGridView and view result
    End Sub

    'Delete record
    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        cmd = New SqlCeCommand("Delete * From Users Where name='Martin'", con)
        If con.State = ConnectionState.Closed Then con.Open()
        cmd.ExecuteNonQuery()
        ShowData() 'Rebinding to DataGridView and view result
    End Sub

    ' Dispose Database Connection object  
    Private Sub Form4_FormClosed(ByVal sender As System.Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles MyBase.FormClosed
        con.Close()
        con = Nothing
    End Sub

End Class



Remember:
You can't import a namespace if you haven't referenced an assembly that contains at least one member of that namespace. Go to the References page of the project properties and reference the SQL Server CE assembly first. Then you can import the SQL Server CE namespace.