Question

我在类中定义了一个dataTable：

def calculate_price(wood_type, drawers):
    # wood_type = get_wood_type()
    # drawers = get_drawers()
    wood_price = 0
    drawer_price = 0

    # ... other calulations

    return drawer_price + wood_price

def display_price(wood, drawer_count):
    price = calculate_price(wood, drawer_count)

    ### Either do this here, or pass in via the main method below
    # wood = get_wood_type()
    # drawer_count = get_drawers()

    print("The amount of drawers you requested were: ", drawer_count, ". Their total was ", drawer_count * 30, ".")
    print("The type of would you requested was ", wood, ". The total for that was ", drawer_count * 30 - price, ".")
    print("Your total is: ", price)

if __name__ == '__main__':

    wood = get_wood_type()
    drawer_count = get_drawers()

    display_price(wood, drawer_count)

当我的主表单加载时，我创建了DataTable的结构，如下所示：

Public Shared Positions As DataTable

PositionX，PositionY和PositionZ的值随时间而变化，我想使用作为主键的hash值在DataTable中更新它们。

但是，我似乎无法正确理解语法。本文（https://msdn.microsoft.com/en-us/library/tat996zc.aspx）表明这种方法可行：

Function createTable()
    ' Function to create datatable structure
    Dim table As New DataTable

    ' Define primary key
    Dim keys(0) As DataColumn
    Dim keyColumn As New DataColumn()
    keyColumn.ColumnName = "hash"
    keys(0) = keyColumn

    ' Define columns
    table.Columns.Add(keyColumn)
    table.Columns.Add("PositionX", GetType(String))
    table.Columns.Add("PositionY", GetType(String))
    table.Columns.Add("PositionZ", GetType(String))

    return table
End Function

但将其应用于我的代码：

Dim customerRow() As Data.DataRow
customerRow = DataSet1.Tables("Customers").Select("CustomerID = 'ALFKI'")

customerRow(0)("CompanyName") = "Updated Company Name"
customerRow(0)("City") = "Seattle"

在前两行“Globals.Positions.DataRow not defined”和“Tables不是DataTable的成员”中给出错误。

我需要做什么才能获得包含我正在寻找的主键值的行，以便我可以更新一些列值？

Answer 1

也许在DataTable的类中有一个属性，设置它，加载数据。有一种方法可以在一行中查找和设置值，例如

Public Class Demo1
    Public Property DataTable As DataTable
    ''' <summary>
    ''' Fire off create and load tabe
    ''' </summary>
    Public Sub New()
        CreateTable()
        LoadData()
    End Sub
    Public Sub CreateTable()
        DataTable = New DataTable
        DataTable.Columns.Add(New DataColumn With {.ColumnName = "hash", .DataType = GetType(String)})
        DataTable.Columns.Add(New DataColumn With {.ColumnName = "PositionX", .DataType = GetType(String)})
        DataTable.PrimaryKey = New DataColumn() {DataTable.Columns("hash")}

    End Sub
    Public Sub LoadData()
        DataTable.Rows.Add(New Object() {"22DE43AS"})
        DataTable.Rows.Add(New Object() {"44DE43AB"})
        DataTable.Rows.Add(New Object() {"33DE43AW"})
    End Sub
    ''' <summary>
    ''' Simple demo to find and update a row
    ''' </summary>
    ''' <param name="hash"></param>
    ''' <param name="PositionX"></param>
    ''' <returns></returns>
    Public Function SetItem(ByVal hash As String, PositionX As String) As Boolean
        Dim result As DataRow() = DataTable.Select($"hash = '{hash}'")
        If result.Count > 0 Then
            result.First.SetField(Of String)("PositionX", PositionX)
            Return True
        Else
            Return False
        End If
    End Function
End Class

演示

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim demo As New Demo1
    If demo.SetItem("44DE43AB", "new value") Then
        MessageBox.Show("Success")
    Else
        MessageBox.Show("Failed")
    End If
End Sub

Answer 2

您可以改为使用Dictionary：

Class Point3D
    Public X, Y, Z As Integer
End Class

Sub test()
    Dim Positions As New Dictionary(Of String, Point3D)         ' create
    Positions("44DE43AB") = New Point3D With {.X = 1, .Y = 2}   ' add
    Positions("44DE43AB").Z = 3                                 ' edit
    Positions.Remove("44DE43AB")                                ' remove
End Sub

DataTable使用主键更新某些列

2 个答案: