从 DBNull 类型到 String 类型的转换在 vb.net 中无效
Conversion from type DBNull to type String is not valid in vb.net
请解决我遇到错误“从类型 'DBNull' 转换为类型 'String' 因为 pathhelper 列具有空值
Private Sub gridView1_CustomUnboundColumnData(ByVal sender As Object, ByVal e As DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs) Handles GridView1.CustomUnboundColumnData
If e.Column.FieldName = "Image" AndAlso e.IsGetData Then
Dim view As GridView = TryCast(sender, GridView)
Dim colorName As String = CStr(view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Color"))
Dim fileName As String = GetFileName(colorName).ToLower()
***Dim PATHHELPER As String = CStr(view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper")) 'error this line***
If (Not Images.ContainsKey(fileName)) Then
Dim img As Image = Nothing
Try
Dim filePath As String = DevExpress.Utils.FilesHelper.FindingFileName(parentpathimage & PATHHELPER, fileName, False)
img = Image.FromFile(filePath)
Catch
End Try
Images.Add(fileName, img)
End If
e.Value = Images(fileName)
End If
End Sub
End Class
我认为像这样的东西应该可以解决问题。可能更好的方法来做到这一点,但这是我想要的方式
Dim PATHHELPER as String = String.Empty
If view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper") <> DBNull.Value Then
PATHHELPER = view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper").ToString
End if
使用 DBNull class 值 属性 进行比较。
Dim PATHHELPER As String
If Not DBNull.Value.Equals(View.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper")) Then
PATHHELPER = CStr(View.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper"))
Else
PATHHELPER = String.Empty 'or Nothing depending what comes next.
End If
请解决我遇到错误“从类型 'DBNull' 转换为类型 'String' 因为 pathhelper 列具有空值
Private Sub gridView1_CustomUnboundColumnData(ByVal sender As Object, ByVal e As DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs) Handles GridView1.CustomUnboundColumnData
If e.Column.FieldName = "Image" AndAlso e.IsGetData Then
Dim view As GridView = TryCast(sender, GridView)
Dim colorName As String = CStr(view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Color"))
Dim fileName As String = GetFileName(colorName).ToLower()
***Dim PATHHELPER As String = CStr(view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper")) 'error this line***
If (Not Images.ContainsKey(fileName)) Then
Dim img As Image = Nothing
Try
Dim filePath As String = DevExpress.Utils.FilesHelper.FindingFileName(parentpathimage & PATHHELPER, fileName, False)
img = Image.FromFile(filePath)
Catch
End Try
Images.Add(fileName, img)
End If
e.Value = Images(fileName)
End If
End Sub
End Class
我认为像这样的东西应该可以解决问题。可能更好的方法来做到这一点,但这是我想要的方式
Dim PATHHELPER as String = String.Empty
If view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper") <> DBNull.Value Then
PATHHELPER = view.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper").ToString
End if
使用 DBNull class 值 属性 进行比较。
Dim PATHHELPER As String
If Not DBNull.Value.Equals(View.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper")) Then
PATHHELPER = CStr(View.GetListSourceRowCellValue(e.ListSourceRowIndex, "Pathhelper"))
Else
PATHHELPER = String.Empty 'or Nothing depending what comes next.
End If