VB 可以分散到像 FoxPro 这样的变量吗？

Question

我需要把一些用 VisualFoxPro 编写的代码用 VB 重写。由于没有使用 FoxPro 的经验，我询问了代码中使用的一些命令，并找到了一个特殊用途的命令：scatter memvar，它从 table 中的列创建了单独的变量。 VB 是否具有等效功能，或者我是否需要使用 Dim 语句创建每个变量？

编辑：我应该提到我正在寻找使用它来传播数据tables，非常抱歉。稍后在 VFP 程序中 insert into memvar 将变量匹配到它们各自的列。我希望避免需要以下方法：

For Each row As DataRow in MyTable
    row.Item(0,i) = myVar1
    row.Item(1,i) = myVar2
    'etc.
    i += 1
Next

遗憾的是，以上是我输入大部分数据的方式。

编辑：为了回应@DRapp 的评论，我正在使用VB 读取.xin 文件并从其代码中形成访问数据table。 .xin 文件中有两个 "collections" 是我感兴趣的：<NamedSymbologyCollection> 和 <FeatureStylesCollection>。这两个集合都在文件的同一行中，所以我编写了代码来逐个标记，挑选出我想要的信息，并将其添加到临时数据 table.

Do Until reader.EndOfStream
    content = reader.ReadLine
    For Each code In content
        If content.Length > 0 Then
            crntTag = content.Substring(0, content.IndexOf(">") + 1)

            If crntTag.Contains("/FeatureStyleCollection>") Then
                Exit Do
            End If

            If crntTag.Contains("<NamedSymbology ItemName") Then
                wholeTag = GetFullLine(content)

                xinCompile.Rows.Add()
                    For Each entry In wholeTag
                        lcstring = wholeTag.Substring(0, wholeTag.IndexOf(">") + 1)

                        If wholeTag.Length = 0 Then
                            Exit For
                        End If

                        If lcstring.Contains("<NamedSymbology ") Then
                                    SymbName = GrabCodeElement(lcstring, "ItemName=")
                                    SymbDesc = GrabCodeElement(lcstring, "Description=")
                                    wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                                    xinCompile.Rows(i).Item("symbName") = SymbName
                                    xinCompile.Rows(i).Item("symbDesc") = SymbDesc
                        ElseIf lcstring.Contains("<BasePointSymbology ") Then
                                    CellLayer = GrabCodeElement(lcstring, "CellLayerName=")
                                    CellName = GrabCodeElement(lcstring, "Name=")
                                    wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                                    xinCompile.Rows(i).Item("cellLayer") = CellLayer
                                    xinCompile.Rows(i).Item("cellName") = CellName
                        ElseIf lcstring.Contains("<LineSymbology ") Then
                                    LineSymb = GrabCodeElement(lcstring, "<LineSymbology LayerName=")
                                    LineSymb = LineSymb.Substring(15, LineSymb.Length - 16)
                                    xinCompile.Rows(i).Item("lineSymb") = LineSymb
                                    wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                        Else
                                    wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                        End If
                    Next
                i += 1
            ElseIf crntTag.Contains("<FeatureStyle ItemName") Then
                wholeTag = GetFullLine(content)
                j = 0

                featStyles.Rows.Add()
                For Each entry In wholeTag
                    lcstring = wholeTag.Substring(0, wholeTag.IndexOf(">") + 1)

                    If wholeTag.Length = 0 Then
                        Exit For
                    End If

                    If lcstring.Contains("<FeatureStyle ") Then
                        SymbName = GrabCodeElement(lcstring, "ItemName=")
                        SymbDesc = GrabCodeElement(lcstring, "Description=")

                            For Each item As DataRow In xinCompile.Rows
                                If SymbName = item.Item("symbName") Then
                                    found = True
                                    Exit For
                                End If
                                j += 1
                            Next

                            If found = True Then
                                wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                            Else
                                Exit For
                            End If

                            xinCompile.Rows(j).Item("symbDesc") = SymbDesc
                    ElseIf lcstring.Contains("<SurveyFeature ") Then
                        NumCode = GrabCodeElement(lcstring, "NumericCode=")
                        DTMexclude = GrabCodeElement(lcstring, "ExcludeFromTriangulation=")
                        lineToPrev = GrabCodeElement(lcstring, "LineToPrevious=")
                        featType = GrabCodeElement(lcstring, "FeatureType=")

                        wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                        xinCompile.Rows(j).Item("numCode") = NumCode
                        xinCompile.Rows(j).Item("DTMexclude") = DTMexclude
                        xinCompile.Rows(j).Item("lineToPrev") = lineToPrev
                        xinCompile.Rows(j).Item("featType") = featType
                    ElseIf lcstring.Contains("<Attribute ") Then
                        LineLayer = GrabCodeElement(lcstring, "Name=")
                        wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                    ElseIf lcstring.Contains("<AlphaCode") Then
                        alphacode = GrabCodeElement(lcstring, "Code=")
                            If IsDBNull(xinCompile.Rows(j).Item("alphaCode")) Then
                                fullAlpha = ""
                                xinCompile.Rows(j).Item("alphaCode") = alphacode
                            Else
                                fullAlpha = xinCompile.Rows(j).Item("alphaCode")
                                xinCompile.Rows(j).Item("alphaCode") = fullAlpha & "," & alphacode
                            End If
                        wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                    Else
                        wholeTag = wholeTag.Remove(wholeTag.IndexOf(lcstring), wholeTag.IndexOf(">") + 1)
                    End If
                Next
            End If
            content = content.Remove(0, crntTag.Length)
        Else
            Exit For
        End If
    Next
Loop

如果您对如何改进上述任何内容有任何建议，请告诉我。

Answer 1

首先，我从来没有用过 FoxPro 或 Visual FoxPro，所以不要指望我所说的在每种情况下都能完美工作。查看 this MSDN page，似乎要在 FoxPro 中执行简单的分散命令，您会使用如下内容：

SCATTER FIELDS LIKE A*,P* EXCEPT PARTNO* TO myArray

以上看起来只是获取所有以 A* 和 P* 开头的字段，并从结果中排除匹配 PARTNO* 的项目。我认为这最好转换为使用 LINQ 查询，它可以 return 一个 Object() 数组。

Dim testTable As New DataTable
Dim myArray As Object()

myArray = From rowItem In (From row As DataRow In testTable.Rows Select row.ItemArray) _
          Where (rowItem.ToString.StartsWith("A") Or rowItem.ToString.StartsWith("P")) _
                And Not rowItem.ToString.StartsWith("PARTNO") Select rowItem

如果您开始更复杂地使用分散命令将值分解为一个新对象，该对象具有与原始 table 中的列相同的属性，那么VB 等价物变得更加困难，因为您必须制作一个继承 System.Dynamic.DynamicObject class 的 class。所以这个例子来自 the MSDN page

CREATE TABLE Test FREE ;
   (Object C(10), Color C(16), SqFt n(6,2))

SCATTER MEMVAR BLANK
m.Object="Box"
m.Color="Red"
m.SqFt=12.5
APPEND BLANK
GATHER MEMVAR
BROWSE

在VB中变得一团糟。我将提供一个非常基本的示例，它非常简单，但希望它能让您了解从哪里开始。

Imports System.Dynamic

Private Class myDynObj : Inherits DynamicObject
    Private internalDict As Dictionary(Of String, Object)

    Public Sub New()
        internalDict = New Dictionary(Of String, Object)
    End Sub

    Public Sub AddProperty(ByVal PropertyName As String, Optional ByVal Value As Object = Nothing)
        addOrSetProperties(New KeyValuePair(Of String, Object)(PropertyName, Value))
    End Sub

    Public Sub addOrSetProperties(ByVal ParamArray newPropertyValuePairs() As KeyValuePair(Of String, Object))
        For Each kvPair As KeyValuePair(Of String, Object) In newPropertyValuePairs.Where(Function(x) Not IsNothing(x.Key))
            If internalDict.ContainsKey(kvPair.Key) Then
                internalDict.Item(kvPair.Key) = kvPair.Value
            Else
                internalDict.Add(kvPair.Key, kvPair.Value)
            End If
        Next
    End Sub

    Public Overrides Function GetDynamicMemberNames() As IEnumerable(Of String)
        Return internalDict.Keys.ToList.Cast(Of String)()
    End Function

    Public Overrides Function TryGetMember(binder As GetMemberBinder, ByRef result As Object) As Boolean
        Return internalDict.TryGetValue(binder.Name, result)
    End Function

    Public Overrides Function TrySetMember(binder As SetMemberBinder, value As Object) As Boolean
        internalDict(binder.Name) = value
        Return True
    End Function

End Class

以及上面的用法class：

Dim testTable As New DataTable("TheTable")
testTable.Columns.Add("foo")
testTable.Columns.Add("bar")
testTable.Columns.Add("Blargh")

Dim columnNames As New List(Of String)(From column As DataColumn In testTable.Columns Select column.ColumnName)

Dim m As Object = New myDynObj
columnNames.ForEach(Sub(x) DirectCast(m, myDynObj).AddProperty(x))

Console.WriteLine(String.Format("The current properties of the object are as follows: {0}", String.Join(", ", DirectCast(m, myDynObj).GetDynamicMemberNames.Cast(Of String))))
Console.WriteLine()

m.foo = "hoopla" : m.Blargh = 654219 : m.waffles = "I'm New!"

Console.WriteLine("And now the values are:")
DirectCast(m, myDynObj).GetDynamicMemberNames.ToList.ForEach(Sub(x) Console.WriteLine(String.Format("{0}, {1}", x, CallByName(m, x, CallType.Get, Nothing))))
Console.WriteLine()


testTable.Rows.Add(m.foo, m.bar, m.Blargh)
Console.WriteLine("XML result:")
Using sw As New StreamWriter(Console.OpenStandardOutput())
    sw.AutoFlush = True
    Console.SetOut(sw)
    testTable.WriteXml(sw, XmlWriteMode.WriteSchema)
End Using

Console.ReadLine()

Answer 2

SCATTER 命令是 Foxpro 的遗留物，没有本机对象化数据。只需在 dotnet 编程中直接访问 recordset/dataset。

VB 可以分散到像 FoxPro 这样的变量吗？

Can VB scatter to variables like FoxPro?

vb.net

foxpro

equivalent

visual-foxpro