OnTextChanged得到错误 [英] OnTextChanged get error

问题描述

  private   void  txt_money_TextChanged（对象发​​件人，EventArgs e）
 {
  double  price =  Double  .Parse（dataGridView1.CurrentRow.Cells [  Price]。Value.ToString（ ））; 
  double  getoil; 
  double  money =  Double  .Parse（txt_money.Text）; 
 getoil = price / money; 
 lb_getoil.Text =   + getoil; 
 lb_allpay.Text = txt_money.Text; 
} 

我的代码我收到错误

 对象引用 set 为 object的实例。

at

  double  price =  Double  .Parse（dataGridView1.CurrentRow.Cells [ 价格]。Value.ToString（））; 

如何解决？

解决方案

请记住每次Text属性获取新值时都会触发Textbox.TextChanged事件 - 因此您将在程序开始时获得一个，而系统的其余部分是设置好或不。



请检查您的代码：

 dataGridView1.CurrentRow。单元格[ 价格]。Value.ToString（）

是否有CurrentRow？在程序开始时，可​​能没有，因为DataGridView还没有填充数据。首先检查：

  private   void  txt_money_TextChanged（ object  sender，EventArgs e）
 {
  if （dataGridView1.CurrentRow ！=  null ）
 {
 ... 
} 
} 

private void txt_money_TextChanged(object sender, EventArgs e)
        {
            double price = Double.Parse(dataGridView1.CurrentRow.Cells["Price"].Value.ToString());
            double getoil;
            double money = Double.Parse(txt_money.Text);
            getoil = price / money;
            lb_getoil.Text = "" + getoil;
            lb_allpay.Text = txt_money.Text;
        }

This my code i got error

Object reference not set to an instance of an object.

at

double price = Double.Parse(dataGridView1.CurrentRow.Cells["Price"].Value.ToString());

How to fix ?

解决方案

Bear in mind that the Textbox.TextChanged event gets fired each time teh Text property gets a new value - so you will get one at the start of your program, wether the rest of your system is set up for it yet or not.

So check in your code:

dataGridView1.CurrentRow.Cells["Price"].Value.ToString()

Is there a CurrentRow? At the start of your program, there probably isn't, because the DataGridView has not been filled with data yet. So check first:

private void txt_money_TextChanged(object sender, EventArgs e)
        {
            if (dataGridView1.CurrentRow != null)
            {
                ...
            }
        }

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