如何给null的字符串赋值

[billlyh]

NowTime = System.DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")
For Each dr As DataGridViewRow In Me.DataGridView1.Rows
Dim cbx As DataGridViewCheckBoxCell = DirectCast(dr.Cells(0), DataGridViewCheckBoxCell)
If CBool(cbx.FormattedValue) Then
'MessageBox.Show(dr.Cells(1).Value.ToString())

Dim sGUID2 As String = System.Guid.NewGuid.ToString()
Dim insert_DataGridView1 As String
insert_DataGridView1 = "insert into PUB.UD33(Key1,Number01,Character01,Character02,Character03,Character04,Character05,Character06," + _
"Character07,Character08,Date01,Character09,Character10,Character11,Character12,Character13,Character14,Character15" + _
") values('" + sGUID2.ToString() + "','" + int_Number01.ToString() + "','" + dr.Cells(1).Value.ToString() + "'," + _
"'" + dr.Cells(2).Value.ToString() + "','" + dr.Cells(3).Value.ToString() + "','" + dr.Cells(4).Value.ToString() + "'," + _
"'" + dr.Cells(5).Value.ToString() + "','" + dr.Cells(6).Value.ToString() + "','" + dr.Cells(7).Value.ToString() + "'," + _
"'" + dr.Cells(8).Value.ToString() + "','" + NowTime + "','" + dr.Cells(9).Value.ToString() + "','" + dr.Cells(10).Value.ToString() + "',"

+ _
"'" + dr.Cells(11).Value.ToString() + "','" + dr.Cells(12).Value.ToString() + "','" + dr.Cells(13).Value.ToString() + "'," + _
"'" + dr.Cells(14).Value.ToString() + "','" + dr.Cells(15).Value.ToString() + "')"
'MessageBox.Show(NowTime)
Me.TextBox1.Text = insert_DataGridView1
'lyh_odbc1.Get_DataTable(insert_DataGridView1)


End If
运行时报错，指向insert_DataGridView1 =...........这一句，
提示“未将对象引用设置到对象的实例。”


仔细检查，是有几个dr.Cells为null的原因，

1-5列是通过
datagridview/属性/杂项/Columns/Collection 添加的，

想给这几列赋值的，但却没成功
If dr.Cells(1).Value.ToString() Is Nothing Then
dr.Cells(1).Value = "未输入 "
End If
系统还是提示dr.Cells(1).Value未将对象引用调协到对象的实例

哪位帮帮我呀

[liuyileneal]

 If dr.Cells(1).Value Is Nothing Then  
  dr.Cells(1).Value = "未输入 "  
  End If  

试一试

[娃都会打酱油了]

If dr.Cells(1).Value Is Nothing Then

[harry999]

判断HasValue属性

[billlyh]

1、２楼，你们是对的，为什么要去了tostring()

[liuyileneal]

dr.Cells(1).Value
因为它是空的，所以用它去调用函数，就会造成空引用