TextBox - 对象引用未设置为对象的实例 [英] TextBox - Object Reference Not Set To An Instance of an Object

问题描述

我有一段非常简单的代码，它抛出了一个意外错误，我正在努力理解可能是什么错误.

I have a very simple piece of code that is throwing an unexpected error and I am struggling to understand what could possibly be wrong.

private void dataNames_CellDoubleClick(object sender, DataGridViewCellEventArgs e) 
{   
    DataGridViewRow row = dataNames.CurrentCell.OwningRow;
    string val = row.Cells["Name"].Value.ToString();
    txtName.Text = val;
}

对象 dataNames 是一个 DataGridView，其中只有一个名为 Names 的列.

The Object dataNames is a DataGridView with only a single Column in it called Names.

当我从网格中双击一个名称时，我希望它填充文本框 (txtName)

When I double click a Name from the Grid I want it to populate the Textbox (txtName)

我看不到文本框如何生成未设置对象"..' 当我所做的只是向其 Text 属性发布值时出现错误.当我遍历字符串 'val' 时，确实从 DataGridView 中获取了正确的值.

I fail to see how a Textbox can produce an 'Object not set . . ' error when all I am doing is posting a value to its Text property. When I step through the string 'val' does pick up the correct value from the DataGridView.

推荐答案

具有讽刺意味的是，花了很长时间找不到问题，我在发布问题后直接找到了.

Ironically, having spent a good while unable to find the problem, I go and spot it straight after posting the question.

该错误发生在 Form_Load 事件的前面，该事件调用自定义 ClearForm 方法，该方法将表单上的所有文本字段清空.但是我做了以下事情:-

The error is earlier in the Form_Load event, which calls a custom ClearForm method, which blanks all text fields on the form. However I had done the following :-

txtTitle.Text = null;
txtAge.Text = null;
txtName = null;

因此我将文本框本身设置为 null，而不是它的文本属性.

Hence I set the textbox itself = null, rather than its text property.

有时最简单的错别字也会产生最令人费解的错误！

Sometimes the simplest of typos produces the most puzzling of errors!

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