检查空值的绑定数据表 vb.net [英] check bound datatable for null value vb.net

问题描述

我目前正在使用带有 sql 后端的 vb.net windows 窗体应用程序.我有两个数据表，它们绑定到两个独立的 sql 语句，并且都返回两个非常简单的数据表.我只需要独立检查两个表中的任何一个中是否存在空值.第一个查询返回单个值，实际上是单个单元格.我一直在 dgv 中使用以下代码来检查 null

I am currently working in vb.net windows form applications with an sql back end. I have two datatables that are bound to two independent sql statements and both return two very simple datatables. I just need to check to see if there is a null value in either of the two tables, independently. The first query returns a single value, literally a single cell. I have always used the following code in a dgv to check for null

Dim Check As Integer = dt.Rows(1).cells(1).value

然而这在这里不起作用，这似乎是因为数据类型是整数.通常使用 DGV，我正在执行点击事件，并从最终用户可以看到的 dgv 中拉取.

However this is not working here, it seems to be because the data type is an integer. Usually with a DGV I am doing a click event and am pulling from a dgv an end user can see.

第二个 sql 查询只有 2 个单元格.因为它有 2 行和 1 列，我需要检查两个单元格以确保它们都不为空.

The second sql query is just 2 cells. As in it has 2 rows and one column and I need to check both cells to make sure neither of them are null.

我一直在网上四处寻找，但找不到任何对我有用的东西.

I have been looking around online but I cant find anything that seems to work for me.

------------------------更新----------------------------

------------------------update----------------------------

 Public Shared Function ToInt32(Value As Object) As Integer
    If DBNull.Value.Equals(Value) Then
        Return 0
    Else
        Return Convert.ToInt32(Value)
    End If
End Function



  Dim ncheck As Integer
  ncheck = SafeConvert.ToInt32(dt.Rows(1)(1))

我将如何在 if 语句中使用此 ncheck 来运行退出子程序和消息框?在我看来，如果 ncheck 不是整数，它只会让我崩溃.

How would i use this ncheck in a if statement to run an exit sub and a message box? It seems to me if ncheck is not an integer it is just going to crash on me.

推荐答案

use DbNull.Value:

   If Not DbNull.Value.Equals(dt.Rows(1).Item(1).value) Then 
      ' do something
   Else 
      ' do something else 
   End If

或使用

If dt.Rows(1).Item(1).value=DbNull.Value

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