resultsetform.vb

Microsoft Mobile Development Handbook的代码,有C#,VB,C++的

Imports System.Data.SqlServerCe
Imports System.ComponentModel
Imports System.Text

Public Class ResultSetForm

    Private Sub MenuItem1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuItem1.Click
        DoStuffWithResultSet()
    End Sub

    Private Const SSCE_M_KEYDUPLICATE As Integer = 25016

    Private Sub DoStuffWithResultSet()

        Dim connectionString As String = "Data Source =" _
        & System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase) _
        & "\MyDatabase.sdf; Password =""MobileP@ssw0rd"";"

        ' Create the ResultSets using our own constructor, to override the default behavior
        Using prodCatRS As ProductCategoryResultSet = _
            New ProductCategoryResultSet(False, connectionString)
            Using productRS As ProductResultSet = _
                New ProductResultSet(False, connectionString)

                Try
                    ' Open the two ResultSets
                    prodCatRS.OpenEx()
                    productRS.OpenEx()

                    ' Report count of records to the screen...
                    ReportRecords(prodCatRS.Connection, productRS)

                    ' SECOND: Add some product categories
                    ' To make sure we don't duplicate names, productCategory.Name has a unique constraint
                    Try
                        prodCatRS.AddProductCategoryRecord("Rock Climbing Equipment")
                        prodCatRS.AddProductCategoryRecord("Scuba Diving Equipment")
                        textBox1.Text += "\r\nProduct Categories added.\r\n"
                    Catch sqlEx As System.Data.SqlServerCe.SqlCeException
                        If sqlEx.NativeError = SSCE_M_KEYDUPLICATE Then
                            ' If the categories already exist, just continue
                            textBox1.Text += "\r\nProduct Category addition failed, items already exist.\r\n"
                        Else
                            Throw
                        End If
                    End Try

                    ' THIRD: Add some products in the category with categoryID of 1
                    productRS.AddProductRecord("Contoso Single Rope", "Red/Blue", 155.95, "60m", 1)
                    productRS.AddProductRecord("Contoso Rock Shoes", "Black", 89.95, "8", 1)
                    textBox1.Text += "\r\nProducts added.\r\n"

                    ' Report count of records to the screen...
                    ReportRecords(prodCatRS.Connection, productRS)
                Finally
                    ' Close the DataReaders
                    productRS.Close()
                    prodCatRS.Close()
                    ' Close and dispose of the database connections
                    productRS.Connection.Close()
                    prodCatRS.Connection.Close()
                End Try
            End Using
        End Using
    End Sub

    Private Sub ReportRecords(ByVal conn As SqlCeConnection, ByVal productRS As ProductResultSet)
        Dim categoryCount As Integer
        ' One way of counting the records is to ask the database
        Using cmd As SqlCeCommand = New SqlCeCommand("SELECT COUNT(*) FROM ProductCategory", conn)
            categoryCount = CType(cmd.ExecuteScalar(), Integer)
        End Using

        ' Alternatively, Get count by casting the ResultSet to IListSource
        Dim productCount As Integer = (CType(productRS, IListSource)).GetList().Count

        Dim sb As StringBuilder = New StringBuilder(textBox1.Text)
        sb.Append("There are currently ")
        sb.Append(categoryCount)
        sb.Append(" product categories.\r\n")
        sb.Append("There are currently ")
        sb.Append(productCount)
        sb.Append(" products.\r\n")
        textBox1.Text = sb.ToString()
    End Sub

End Class