Question

我知道这个标题下有文章，但我不能将它们与我的错误联系起来。我正在尝试拼凑一个模拟查询页面作为Uni任务的一部分，并偶然发现了我已经修改过的脚本。有两种形式，一种是对数据网格运行集合查询 - 这可以工作，但在下面的另一个页面脚本上有这个NullReferenceException。代码与工作表格完全相同，所以出了什么问题？

Public Class Adding_Information

'Dim SQL As New SQLControl
Private SQL As New SQLControl
Public Property DGV_SetQueries As Object



Private Sub btnCustomerFind_Click(sender As Object, e As EventArgs) Handles btnCustomerFind.Click
    If txtCustomerName.Text <> "" Then

        If SQL.HasConnection = True Then
            Dim dgv_QueryData As Object = Nothing
            dgv_QueryData.DataSource = SQL.SQLDataset.Tables(0)
            'Create a query variable
            Dim query As String = "Select
                              Customer.Title,
                              Customer.Firstname,
                              Customer.Surname,
                              Customer.Email,
                              Customer.MobileNo,
                              Customer.Postcode,
                              Customer.Regno
                            From
                              Customer
                            Where
                              Customer.Surname = 'Fletcher'
                            Order By
                              Customer.Firstname"

            SQL.RunQuery(query)

            If SQL.SQLDataset.Tables.Count > 0 Then

                'ensure that there is only one table
                DataGridView1.DataSource = SQL.SQLDataset.Tables(0)

            End If

        End If

    End If

End Sub

Private Sub DGV_SetQueries_CellContentClick(sender As Object, e As DataGridViewCellEventArgs)

End Sub

Private Sub DataGridView1_CellContentClick(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick

End Sub
End Class

DataGridView被称为datagridview1，hasconnection是对SQL服务器的连接检查。有没有人发现过什么？

Answer 1

Dunno，如果这应该是一个答案或评论，但......错误很明显。

    If SQL.HasConnection = True Then
        Dim dgv_QueryData As Object = Nothing
        dgv_QueryData.DataSource = SQL.SQLDataset.Tables(0)

您正在初始化＆＃39; dgv_QueryData＆＃39;没有什么＆＃39;然后立即使用它，试图访问其数据源＆＃39;属性...你必须将它初始化为某个东西，或者是另一个变量，或者是新的＆＃39; ...

VB NullReferenceException未处理

1 个答案: