当我尝试在 asp.net Detailsview 中添加插入值时，我得到了 "Object reference not set to an instance of an object"

Question

我该怎么做才能修复 "Object reference not set to an instance of an object" 错误。它指的是哪个对象？代码：

Private Sub dvSMasterCurrentYear_DataBound(sender As Object, e As EventArgs) Handles dvSMasterCurrentYear.DataBound
    Dim dv As DetailsView = New DetailsView
    If DetailsViewMode.Insert Then
        DirectCast(dv.FindControl("PlantYear"), TextBox).Text = GetYear()
    End If
End Sub

获取年份returns为当前年份，它出现在detailsview文本框中"PlantYear"。我尝试使用上面的代码插入值。

感谢您的帮助。

Answer 1

很可能 FindControl 实际上并未找到控件。签入以确保它确实找到了您想要找到的内容是明智的：

Private Sub dvSMasterCurrentYear_DataBound(sender As Object, e As EventArgs) Handles dvSMasterCurrentYear.DataBound
    Dim dv As DetailsView = New DetailsView
    If DetailsViewMode.Insert Then
        Dim ctl = dv.FindControl("PlantYear")
        If ctl IsNot Nothing Then
            DirectCast(dv.FindControl("PlantYear"), TextBox).Text = GetYear()
        Else
            Throw New Exception("Control was not found")
        End If        
    End If
End Sub

当我尝试在 asp.net Detailsview 中添加插入值时，我得到了 "Object reference not set to an instance of an object"

When I try add insert a value into a asp.net Detailsview I get a "Object reference not set to an instance of an object"

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asp.net

detailsview