使用带有连接字符串的 Datasource(dt).DefaultView.RowFilter 过滤 dgv

如何解决使用带有连接字符串的 Datasource(dt).DefaultView.RowFilter 过滤 dgv

出于某种原因，当我应用我的 dgvBarcodes.Datasource.defaultview.Rowfilter = strDGVBarcodesFilter 时，它正在寻找（“Test”列），而不是过滤“LongDescription=Test”列上的行。这是意料之外的行为。如何让 .defaultview.RowFilter 根据“LongDescription=Test”过滤所有行？

本例中的 strDGVBarcodesFilter = "LongDescription=Test"，当鼠标悬停时，我得到的错误是 "System.Data.EvaluateException: 'Cannot find column [test].'"

事件处理程序：

  If txtLongDescription2.Text IsNot nothing Then
        Dim strLongDescription As String = txtLongDescription2.Text 
        Dim strLongDescriptionFilter As String = ""
        If strLongDescription = "" Then
            strLongDescriptionFilter = ""
        Else
            strLongDescriptionFilter = "LongDescription=" & strLongDescription
        End If
        Dim strDGVBarcodesFilter As String = fnBuildFilterString(strMainBrandFilter,strSubBrandFilter,strLongDescriptionFilter)
        dgvBarcodes.DataSource.defaultview.Rowfilter = strDGVBarcodesFilter
    End If

过滤字符串生成器函数；

Private Function fnBuildFilterString(strFilterComponent1 As String,strFilterComponent2 As String,Optional strFilterComponent3 As String = "",Optional strFilterComponent4 As String = "",Optional strFilterComponent5 As String = "") As String
    'Essentially it builds this; strMainFilter = strFilterComponent1 & " AND " & strFilterComponent2 & " AND " & strFilterComponent3 & " AND " & strFilterComponent4 & " AND " & strFilterComponent5
    Dim strMainFilter As String = "" 'Reset the masterfilter string to be empty

    If strFilterComponent1 <> "" Then  'If the filter component isn't empty
        If strMainFilter = "" Then 'And if the masterfilter is empty
            strMainFilter = strFilterComponent1 'Adds the filter component to the masterfilter string
        Else 'The masterfilter isn't empty
            strMainFilter &= " AND " & strFilterComponent1 'then it adds " AND " &field to the masterfilter string
        End If
    Else 'Filter component is empty,do nothing
    End If 'check next component

    If strFilterComponent2 <> "" Then  'If the filter component isn't empty
        If strMainFilter <> "" Then 'And if the masterfilter isn't empty
            strMainFilter &= " AND " & strFilterComponent2 'then it adds " AND " &field to the masterfilter string
        Else 'The masterfilter is empty
            strMainFilter = strFilterComponent2 'Adds the filter component to the masterfilter string
        End If
    Else 'Filter component is empty,do nothing
    End If 'check next component        

    If strFilterComponent3 <> "" Then  'If the filter component isn't empty
        If strMainFilter <> "" Then 'And if the masterfilter isn't empty
            strMainFilter &= " AND " & strFilterComponent3 'then it adds " AND " &field to the masterfilter string
        Else 'The masterfilter is empty
            strMainFilter = strFilterComponent3 'Adds the filter component to the masterfilter string
        End If
    Else 'Filter component is empty,do nothing
    End If 'check next component

    If strFilterComponent4 <> "" Then  'If the filter component isn't empty
        If strMainFilter <> "" Then 'And if the masterfilter isn't empty
            strMainFilter &= " AND " & strFilterComponent4 'then it adds " AND " &field to the masterfilter string
        Else 'The masterfilter is empty
            strMainFilter = strFilterComponent4 'Adds the filter component to the masterfilter string
        End If
    Else 'Filter component is empty,do nothing
    End If 'check next component

    If strFilterComponent5 <> "" Then  'If the filter component isn't empty
        If strMainFilter <> "" Then 'And if the masterfilter isn't empty
            strMainFilter &= " AND " & strFilterComponent5 'then it adds " AND " &field to the masterfilter string
        Else 'The masterfilter is empty
            strMainFilter = strFilterComponent5 'Adds the filter component to the masterfilter string
        End If
    Else 'Filter component is empty,do nothing
    End If 'check next component

    Return strMainFilter
End Function

解决方法

想想你在那里做什么。如果您在 VB 代码中执行此操作：

Dim someStringVariable As String

'...

If someStringVariable = Test Then

您是否希望将该变量与文字文本“Test”进行比较？当然不是，因为那里没有文字。您必须用双引号将文本括起来以表明它是文字 String。如果您希望在 SQL 代码中使用文字文本（过滤器是 SQL WHERE 子句），那么您需要执行等效操作。如何在 SQL 代码中表示文字文本？带单引号。

这是做您想做的事情的正确方法：

strLongDescriptionFilter = $"LongDescription = '{strLongDescription}'"

和：

Dim criteria As New List(Of String)

If Not String.IsNullOrWhitespace(strFilterComponent1) Then
    criteria.Add(strFilterComponent1)
End If

'Etc.

Return String.Join(" AND ",criteria)

您还可以进行其他改进，但这对于第一步来说可能已经足够了。