如何实现DataGridView的添加删除修改？

1,创建winform窗体应用程序

2，在界面上拖入DataGridView控件

3，添加相应的列如图：

4，开始编写后面的代码：

private DataTable CountryDt = new DataTable();
private DataTable CityDt = new DataTable();

public Main()
{
InitializeComponent();

InitCountryDt();
InitCityDt();
InitGrid();
}

private void InitCityDt()
{
string[] citys = { CN|1|北京, CN|2|天津, CN|3|山西, JP|4|大阪, JP|5|横滨, JP|6|名古屋, JP|7|神户, US|8|纽约
, US|9|洛杉矶, US|10|芝加哥, US|11|休斯敦, US|12|费城, US|13|旧金山};
CityDt.Columns.Add(cityCode);
CityDt.Columns.Add(cityName);
CityDt.Columns.Add(Pid);
for (int i = 0; i < citys.Length; i++)
{
var newRow = CityDt.NewRow();
newRow[cityCode] = citys[i].Split('|')[1];
newRow[cityName] = citys[i].Split('|')[2];
newRow[Pid] = citys[i].Split('|')[0];
CityDt.Rows.Add(newRow);
}
}
private void InitCountryDt()
{
string[] countrys = { CN|中国, JP|日本, US|美国 };
CountryDt.Columns.Add(countryCode);
CountryDt.Columns.Add(countryName);
for (int i = 0; i < countrys.Length; i++)
{
var newRow = CountryDt.NewRow();
newRow[countryCode] = countrys[i].Split('|')[0];
newRow[countryName] = countrys[i].Split('|')[1];
CountryDt.Rows.Add(newRow);
}

}
private void InitGrid()
{
var dt = new DataTable();
dt.Columns.Add(Id);
dt.Columns.Add(CountryCode);
dt.Columns.Add(CityCode);
for (int i = 10; i < 20; i++)
{
var newRow = dt.NewRow();
newRow[Id] = i.ToString();
dt.Rows.Add(newRow);
}
dataGridView1.DataSource = dt;
}

private void btnAdd_Click(object sender, EventArgs e)
{
var dt = dataGridView1.DataSource as DataTable;

var newRow = dt.NewRow();
newRow[Id] = dt.Rows.Count + 1;
dt.Rows.Add(newRow);

for (int i = 0; i < dt.Rows.Count; i++)
{
var countryCell = new DataGridViewComboBoxCell();
countryCell.DataSource = CountryDt;
countryCell.ValueMember = countryCode;
countryCell.displayMember = countryName;
dataGridView1.Rows[i].Cells[countryCode] = countryCell;
}
}

private void dataGridView1_CellValueChanged(object sender, DataGridViewCellEventArgs e)
{
var dt = this.dataGridView1.DataSource as DataTable;
if (dataGridView1.Columns[e.ColumnIndex].Name == nameof(CountryCode))
{
var countryCode = dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value;
var drs = CityDt.Select(Pid=' + countryCode + ');
var newCityDt = new DataTable();
newCityDt.Columns.Add(cityCode);
newCityDt.Columns.Add(cityName);
newCityDt.Columns.Add(Pid);
foreach (DaTarow row in drs)
{
var newRow = newCityDt.NewRow();
newRow[cityCode] = row[cityCode];
newRow[cityName] = row[cityName];
newRow[Pid] = row[Pid];
newCityDt.Rows.Add(newRow);
}
var cityCell = new DataGridViewComboBoxCell();

cityCell.DataSource = newCityDt;
cityCell.displayMember = cityName;
cityCell.ValueMember = cityCode;
dataGridView1.Rows[e.RowIndex].Cells[CityCode] = cityCell;
}
}

private void Main_Load(object sender, EventArgs e)
{
var vdt = dataGridView1.DataSource as DataTable;
for (int i = 0; i < vdt.Rows.Count; i++)
{
var cell = new DataGridViewComboBoxCell()
{
displayMember = countryName,
ValueMember = countryCode,
DataSource = CountryDt
};

dataGridView1.Rows[i].Cells[CountryCode] = cell;
if (i % 2 == 0)
{
dataGridView1.Rows[i].Cells[CountryCode].Value = JP;
dataGridView1.Rows[i].Cells[CityCode].Value = new Random().Next(4, 7);
}
//else {
// dataGridView1.Rows[i].Cells[CountryCode].Value = CN;
//}
if (i % 5 == 0)
{
dataGridView1.Rows[i].Cells[CountryCode].Value = CN;
dataGridView1.Rows[i].Cells[CityCode].Value = new Random().Next(1, 3);
}
if (i % 9 == 0)
{
dataGridView1.Rows[i].Cells[CountryCode].Value = US;
dataGridView1.Rows[i].Cells[CityCode].Value = new Random().Next(8, 13);
}
}
}

private void btnRemove_Click(object sender, EventArgs e)
{

var selected = dataGridView1.SelectedRows;
var dt = dataGridView1.DataSource as DataTable;
if (selected.Count > 0)
{
for (var i = 0; i < selected.Count; i++)
{
var row = selected[i];
dt.Rows.RemoveAt(row.Index);
}
}
}