vb.net 检查数据表值是否为空

Check if Datatable Value is Null

提问by Codemunkeee

Basically, I just want to ask how to check a datatable value if it is null or not? I am looping through each cells on the table, and check if the value of a cell is null.

基本上，我只想问如何检查数据表值是否为空？我正在遍历表格上的每个单元格，并检查单元格的值是否为空。

I tried this

我试过这个

If Not dt.Rows(i)(j).value Is Nothing Then
   MsgBox("cell empty")
End If

and

和

If Not dt.Rows(i)(j).value = "" Then
   MsgBox("cell empty")
End If

but it is not working.

但它不起作用。

As of now, my datatable looks like this

截至目前，我的数据表看起来像这样

"e" means empty

“e”表示空

"ne" means not empty

“ne”表示不为空

"x" dont care

“x”不在乎

---

---

Col1 Col2 Col3 ... 

ne   x    x   ...

x    e    x   ...

x    x    x   ...

examples from the table above..

上表中的例子..

dt(0)(0) = ne

dt(0)(0) = ne

dt(1)(1) = e

dt(1)(1) = e

dt(0)(1) = either "e" or "ne"

dt(0)(1) = "e" 或 "ne"

PS, all the data in the datatable are all strings..

PS，datatable中的所有数据都是字符串..

how can I get the value if dt(1)(1) is empty? C# codes would be okay too..thanks

如果 dt(1)(1) 为空，我如何获得该值？C# 代码也可以..谢谢

EDIT:

编辑：

somehow, I've managed to solve my question by doing this, it met my requirement in my program so.. yea.

不知何故，我通过这样做设法解决了我的问题，它满足了我在程序中的要求，所以..是的。

If dt.Rows(i)(j).Value.ToString = "" Then
   MsgBox("empty")
End If

thanks. Please close the thread.

谢谢。请关闭线程。

回答by Cory

Compare the value to DBNull.Value.

将值与 进行比较DBNull.Value。

foreach(DataRow row in myTable.Rows)
{
    object value = row["column"];
    if (value == DBNull.Value)
        // do something
    else
        // do something else
}

This was also answered on a different question here.

这也回答了一个不同的问题在这里。

回答by Lee Gary

http://msdn.microsoft.com/en-us/library/system.convert.isdbnull(v=vs.110).aspx

http://msdn.microsoft.com/en-us/library/system.convert.isdbnull(v=vs.110).aspx

you can use IsDBNull method

您可以使用 IsDBNull 方法

while (dr.Read())
{
  dr.GetValues(fieldValues);

  for (int fieldCounter = 0; fieldCounter < fieldCount; fieldCounter++)
  {
     if (Convert.IsDBNull(fieldValues[fieldCounter]))
        fieldValues[fieldCounter] = "NA";
  }
  grid.Rows.Add(fieldValues);


 }

回答by V-SHY

For VB.net

对于 VB.net

I found this, sorry I'm not sure what to check inside the IsDbNull (if wrong please forgive me) because I have no experience deal with database in vb.net.

我发现了这个，抱歉，我不确定在 IsDbNull 中检查什么（如果错误，请原谅我），因为我没有在 vb.net 中处理数据库的经验。

If wrong, please comment me to fix it, thanks.

如果错了，请评论我修复它，谢谢。

If NOT IsDbNull(dt.Rows(i)(j)) Then
   MsgBox("cell non-empty")
ELSE
   MsgBox("cell empty")
End If

OR check much more than only DbNull like accepted answer in this post

或者检查不仅仅是 DbNull 像这篇文章中接受的答案

If IsDBNull(dt.Rows(i)(j)) OrElse dt.Rows(i)(j).Value.ToString Is Nothing OrElse dt.Rows(i)(j).Value.ToString = string.Empty Then
   MsgBox("cell empty")

1. If I want to check IsDBNull(), I should put dt.Rows(i)(j)or dt.Rows(i)(j).Valueto check?
2. If I want to check Is Nothing, I should put dt.Rows(i)(j)or dt.Rows(i)(j).Valueor dt.Rows(i)(j).Value.ToStringto check?

1. 如果我想检查IsDBNull()，我应该放dt.Rows(i)(j)还是 dt.Rows(i)(j).Value检查？
2. 如果我要检查Is Nothing，我应该把dt.Rows(i)(j)或 dt.Rows(i)(j).Value或dt.Rows(i)(j).Value.ToString检查？

thanks. Sorry for ask questions in question....

谢谢。抱歉问了有问题的问题......

回答by Manish Parakhiya

You can try following

您可以尝试以下

if(string.IsNullOrEmpty((string)dt.Rows[i][j].value))
{
  MsgBox("cell empty");
}
else
{
 MsgBox("cell is not empty")
}