Question

我有一个名为CarsType.accdb的数据库，数据库Item_Name，Item_Num，Item_Qty，Item_Cost中有四个字段。

我能够让数据库在VisualBasic中显示我的数据，但我不知道如何在我的标签中显示总成本（lblTotalCost）。我更喜欢用VB而不是写入我的访问程序。所有我想做的事情都会成倍增加item_qty * Item_Cost我将如何做到这一点？

Public Class frmCarInventory

    Private Sub CarInventoryBindingNavigatorSaveItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CarInventoryBindingNavigatorSaveItem.Click
        Me.Validate()
        Me.CarInventoryBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.CarDataSet)

    End Sub

    Private Sub frmCarInventory_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'TODO: This line of code loads data into the 'CarDataSet.CarInventory' table. You can move, or remove it, as needed.
        Me.CarInventoryTableAdapter.Fill(Me.CarDataSet.CarInventory)


        Try
            Me.CarInventoryTableAdapter.Fill(Me.CarDataSet.CarInventory)
        Catch ex As Exception
            MsgBox("The Database Files is Unavailable", , "Error")
        End Try



    End Sub

    Private Sub btnComputeTheTotalValueOfInventory_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnComputeTheTotalValueOfInventory.Click


        Dim strSql As String = "SELECT * FROM CarType "

        'strPath provides the database type and path of the CarType database.
        Dim strPath As String = "Provider=Microsoft.ACE.OLEDB.12.0 ;" & "Data Source=..\CarType.accdb"
        Dim odaInventory As New OleDb.OleDbDataAdapter(strSql, strPath)
        Dim DatCost As New DataTable
        Dim intCount As Integer
        Dim decTotalCost As Decimal = 0D

        'The DataTable name datCost is filled with the data
    odaInventory.Fill(DatCost)

        'The connection to the databsise is disconnected
        odaInventory.Dispose()

        For intCount = 0 To DatCost.Rows.Count - 1
            decTotalCost += Convert.ToDecimal(DatCost.Rows(intCount)("Total Inventory  Cost"))
        Next

        Me.lblTotalCost.Visible = True
        Me.lblTotalCost.Text = "El Value " & decTotalCost.ToString("C")

    End Sub
End Class

这会像sql satement一样处理吗？

Answer 1

将新System.Data.DataColumn添加到System.Data.DataTable时，可以指定表达式，从而创建计算列。在C＃中，执行此操作的语法是：

dataTable.Columns.Add("total_cost", typeof(double), "item_qty * item_cost");

在VB.NET中执行此操作的语法非常相似，但我将其留作读者练习。

Answer 2

也许你可以使用这样的东西？

Dim TotalCost As String

TotalCost = Me![item_qty] * Me![item_cost]

Me![lblTotalCost].Caption = TotalCost

如何在.NET中计算数据库列

2 个答案: