如何找出datagridview的复选框值时停止空引用异常？ [英] How to stop null reference exception when finding datagridview checkbox value?

问题描述

我使用的WinForms和C＃,.

I am using winforms and C#,.

当我试图让datagridviewcheckbox状态，如果该复选框不正确显示空引用异常被抓为例外。

When i try to get datagridviewcheckbox state, if the checkbox not true it shows "Null Reference Exception was caught" as Exception.

我的code是

foreach (DataGridViewRow fees_row in this.dataGridView2.Rows)
{
    if ((bool) fees_row.Cells[0].Value == true)
    {
    }
}

该错误是在该行：

The error is in the line:

if ((bool) fees_row.Cells[0].Value == true)

如何设置datagridview的复选框值不为空。或者逃避这种例外。

how to set datagridview checkbox value not null. or escape this exception.

推荐答案

您需要确保该的DataGridViewCell 的对象不是空的第一的，试图询问它的价值了。那是什么导致了的NullReferenceException -you're询问的该值属性空对象！

You need to make sure that the DataGridViewCell object is not null first, before trying to interrogate its value. That's what's causing the NullReferenceException—you're interrogating the Value property of a null object!

更改code看起来是这样的：

Change your code to look like this:

foreach (DataGridViewRow fees_row in this.dataGridView2.Rows)
{
    var cell = fees_row.Cells[0];
    if (cell != null)
    {
        var value = cell.Value;
        if (value != null && (bool)value == true)
        {
            // Do whatever...
        }
    }
}

但在此之前别人留下一个表露无疑评论，但通常不建议对文字真来检查一个布尔值。你所编写的如果（boolValue）

But before someone else leaves a snarky comment, there's generally no reason to check a Boolean value against a literal true. All you have to write is if (boolValue)

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