DataGridView触发current row returns null错误，求代码问题排查

• 报错的核心原因是dataGridView1.CurrentRow为null时你直接访问了它的Cells属性。触发该场景最直接的原因是你点击button3给textBox1赋值时，会立刻触发textBox1_TextChanged事件，此时CurrentRow还未完成上下文绑定或者因为赋值操作导致DataGridView焦点丢失，CurrentRow就会返回null。
• 其他常见触发场景包括：DataGridView未选中任何行、控件尚未完成数据绑定就执行赋值逻辑、开启AllowUserToAddRows属性时选中了底部的空白新增行。
• 现有代码没有做任何空值校验，一旦CurrentRow、Cells对应项为null时，就会直接抛出运行时异常。

首先你需要避免button3给文本框赋值时触发TextChanged事件，同时加上空值判断逻辑，修复后的参考代码如下：

private void button3_Click(object sender, EventArgs e)
{
    // 先解绑TextChanged事件，避免赋值时触发回写
    textBox1.TextChanged -= textBox1_TextChanged;
    textBox2.TextChanged -= textBox2_TextChanged;
    textBox3.TextChanged -= textBox3_TextChanged;
    textBox4.TextChanged -= textBox4_TextChanged;
    textBox5.TextChanged -= textBox5_TextChanged;
    textBox6.TextChanged -= textBox6_TextChanged;

    // 加空值校验和新行判断
    if (dataGridView1.CurrentRow != null && !dataGridView1.CurrentRow.IsNewRow)
    {
        textBox1.Text = dataGridView1.CurrentRow.Cells[0].Value?.ToString() ?? string.Empty;
        textBox2.Text = dataGridView1.CurrentRow.Cells[1].Value?.ToString() ?? string.Empty;
        textBox3.Text = dataGridView1.CurrentRow.Cells[2].Value?.ToString() ?? string.Empty;
        textBox4.Text = dataGridView1.CurrentRow.Cells[3].Value?.ToString() ?? string.Empty;
        textBox5.Text = dataGridView1.CurrentRow.Cells[4].Value?.ToString() ?? string.Empty;
        textBox6.Text = dataGridView1.CurrentRow.Cells[5].Value?.ToString() ?? string.Empty;
    }

    // 重新绑定事件
    textBox1.TextChanged += textBox1_TextChanged;
    textBox2.TextChanged += textBox2_TextChanged;
    textBox3.TextChanged += textBox3_TextChanged;
    textBox4.TextChanged += textBox4_TextChanged;
    textBox5.TextChanged += textBox5_TextChanged;
    textBox6.TextChanged += textBox6_TextChanged;
}

private void textBox1_TextChanged(object sender, EventArgs e)
{
    if (dataGridView1.CurrentRow != null && !dataGridView1.CurrentRow.IsNewRow)
    {
        dataGridView1.CurrentRow.Cells[0].Value = textBox1.Text;
    }
}

private void textBox2_TextChanged(object sender, EventArgs e)
{
    if (dataGridView1.CurrentRow != null && !dataGridView1.CurrentRow.IsNewRow)
    {
        dataGridView1.CurrentRow.Cells[1].Value = textBox2.Text;
    }
}

private void textBox3_TextChanged(object sender, EventArgs e)
{
    if (dataGridView1.CurrentRow != null && !dataGridView1.CurrentRow.IsNewRow)
    {
        dataGridView1.CurrentRow.Cells[2].Value = textBox3.Text;
    }
}

private void textBox4_TextChanged(object sender, EventArgs e)
{
    if (dataGridView1.CurrentRow != null && !dataGridView1.CurrentRow.IsNewRow)
    {
        dataGridView1.CurrentRow.Cells[3].Value = textBox4.Text;
    }
}

private void textBox5_TextChanged(object sender, EventArgs e)
{
    if (dataGridView1.CurrentRow != null && !dataGridView1.CurrentRow.IsNewRow)
    {
        dataGridView1.CurrentRow.Cells[4].Value = textBox5.Text;
    }
}

private void textBox6_TextChanged(object sender, EventArgs e)
{
    if (dataGridView1.CurrentRow != null && !dataGridView1.CurrentRow.IsNewRow)
    {
        dataGridView1.CurrentRow.Cells[5].Value = textBox6.Text;
    }
}

内容的提问来源于stack exchange，提问作者Who Knows