如何在VB6中限制添加重复项

Question

我有一个用 VB6 编写的应用程序。

此应用程序包含一个文件，其中包含包含

foreach

循环的片段。在此循环中，方法将控件添加到一个部分（部分是报告中的一个区域）。

我正在尝试实现以下功能：

当

theheader

添加到

headerSection

中时，

tt

不会再次添加

theHeader

，但是此代码片段无法做到这一点。我哪里错了？

For Each thisColumn As Column In theColumns
  If thisColumn.Type = Column.ColumnType.Description Then
     AddDescriptionColumn(thisColumn, startColumnAt, headerTop)
  End If
 Private Sub AddDescriptionColumn(ByVal ColumnToAdd As Column, ByRef LeftPosition As Single, ByVal HeaderTop As Single)

  'Get report sections
  Dim headerSection As ActiveReports.Section = _theActiveReport.Sections(PageHeaderName)

  'Add column header text
  Dim theHeader As New ActiveReports.Label
  theHeader.Name = "lblDescription"
  theHeader.Text = ColumnToAdd.DisplayCaption
  theHeader.Font = ColumnToAdd.HeaderFont
  theHeader.Location = New PointF(LeftPosition, HeaderTop)
  theHeader.Size = New SizeF(columnWidth, _columnHeaderHeight)
  If TextHeight(ColumnToAdd.DisplayCaption, theHeader.Font, columnWidth) > _columnHeaderHeight Then
     theHeader.VerticalAlignment = ActiveReports.VerticalTextAlignment.Top
  Else
     theHeader.VerticalAlignment = ActiveReports.VerticalTextAlignment.Bottom
  End If
  theHeader.BackColor = Color.Transparent
  theHeader.MultiLine = True
  theHeader.WordWrap = True
  theHeader.Visible = True
  headerSection.Controls.Add(theHeader)

Answer 1

我会尝试这样的事情：

Private Sub AddDescriptionColumn(...
Dim bolFound as boolean=False

'Get report sections
Dim headerSection As ActiveReports.Section = _theActiveReport.Sections(PageHeaderName)

' Iterate through the list of controls. Set bolFound if control name already exists.
For Each control As ARControl In headerSection.Controls
    If control.Name="lblDescription" Then
      bolFound=True
      Exit For
    End If
Next

If bolFound=True Then
  'A control named lblDescription already exists in the headerSection
Else
  'Add column header text
  ...
End If