当我对行进行更改时，为什么DataRowState显示添加而不是修改？

Question

我的程序显示一个带有一些数据的简单数据网格视图：

用户（我）可以更改数据（注意第一行）：

当我查看程序中的数据源时，我可以看到更改的值：

但是，DataRowState是Added而不是Modified。怎么会这样？数据显然已经改变，但DataRowState没有反映这一点：

对于我的生活，我无法弄清楚DataRowState在数据源的每一行上显示Added的原因。以下是我的计划的完整列表：

using System;
using System.Collections.Generic;
using System.Data;
using System.Windows.Forms;

namespace DataBindingTest
{
    using System.ComponentModel;

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            // Create some people and a list to hold them.
            var personA = new Person { Name = "Kevin", Address = "140 Holiday Drive" };
            var personB = new Person { Name = "Donna", Address = "123 Somestreet" };
            var personC = new Person { Name = "Mark", Address = "145 Uptown Blvd" };
            var personD = new Person { Name = "Bryce", Address = "504 Greymere Road" };
            var personE = new Person { Name = "Parzival", Address = "99A Housing Brad St" };
            var people = new List<Person> { personA, personB, personC, personD, personE };

            //// Make a datatable to hold the people

            var tblPeople = new DataTable();
            tblPeople.Columns.Add("Name");
            tblPeople.Columns.Add("Address");

            foreach (var person in people)
            {
                tblPeople.Rows.Add(person.Name, person.Address);
            }

            // Set binding source to the table
            bindingSource1 = new BindingSource();
            bindingSource1.DataSource = tblPeople;
            dataGridView1.DataSource = bindingSource1;
        }

        private void btnUpdate_Click(object sender, EventArgs e)
        {
            // Get only the changed rows
            // (The line below is where the null reference error is occuring because rowstate never == Modified)
            var changedRows = ((DataTable)bindingSource1.DataSource).GetChanges(DataRowState.Modified).Rows;
        }
    }

    public class Person
    {
        public string Name { get; set; }
        public string Address { get; set; }
    }
}

Answer 1

由于您在构造函数中添加了行，因此所有行都具有状态＆＃39;已添加＆＃39;。修改第一个时，它仍然是添加的，这是正常的。您只需接受所有正在运行的数据表中的更改：

   public Form1()
    {
        InitializeComponent();

        // Create some people and a list to hold them.
        var personA = new Person { Name = "Kevin", Address = "140 Holiday Drive" };
        var personB = new Person { Name = "Donna", Address = "123 Somestreet" };
        var personC = new Person { Name = "Mark", Address = "145 Uptown Blvd" };
        var personD = new Person { Name = "Bryce", Address = "504 Greymere Road" };
        var personE = new Person { Name = "Parzival", Address = "99A Housing Brad St" };
        var people = new List<Person> { personA, personB, personC, personD, personE };

        //// Make a datatable to hold the people

        var tblPeople = new DataTable();
        tblPeople.Columns.Add("Name");
        tblPeople.Columns.Add("Address");

        foreach (var person in people)
        {
            tblPeople.Rows.Add(person.Name, person.Address);
        }

        // this line sets the state of the added rows to 'unchanged', 
        // so when you modify one row it becomes'modified'
        tblPeople.AcceptChanges();

        // Set binding source to the table
        bindingSource1 = new BindingSource();
        bindingSource1.DataSource = tblPeople;
        dataGridView1.DataSource = bindingSource1;
    }

我希望它有所帮助。

Answer 2

将行添加到表后，您需要调用

tblPeople.AcceptChanges();

向表中添加行时，其RowState为＆＃34;已添加＆＃34;。当您调用AcceptChanges（）时，其RowState设置为＆＃34; UnChanged＆＃34;。如果您随后编辑行中的单元格，则RowState将更改为＆＃34; Modified＆＃34;在相应的行中，这些行将显示在＆＃34; changedRows＆＃34;在你的事件处理程序中。