在DataGridView指定行添加ComboBox

表格样式
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       列1             ||            列2
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    静态标签      ||         TextBox  
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    静态标签      ||     ComboBox  
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    静态标签      ||     ComboBox  
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代码

       System.Windows.Forms.ComboBox ComboBox1;

        private void Form1_Load(object sender, EventArgs e)
        ...{
            ComboBox1 = new ComboBox();
            ComboBox1.FormattingEnabled = true;
            ComboBox1.Items.AddRange(new object[] ...{
            "1",
            "2",
            "3",
            "4",
            "5",
            "6"});
            ComboBox1.Name = "ComboBox1";
            ComboBox1.TextChanged += new System.EventHandler(this.ComboBox1_TextChanged);
            this.DataGridView1.Controls.Add(this.ComboBox1);

            this.DataGridView1.AllowUserToResizeRows = false;
            this.DataGridView1.AllowUserToResizeColumns = false;
            this.DataGridView1.Columns.Add("Column1", "Column1");
            this.DataGridView1.Columns.Add("Column2", "Column2");
            for (int i = 1; i <= 3; i++)
            ...{
                this.DataGridView1.Rows.Add("行" + i.ToString() + " 列1", "行"+ i.ToString() + " 列2");
            }
            this.ComboBox1.Visible = false;
            
        }
        private void DataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
        ...{
            if (e.ColumnIndex == 1)
            ...{
                switch (e.RowIndex)
                ...{
                    case 1:
                    case 2:
                        this.ComboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
                        break;
                    default:
                        this.ComboBox1.Visible = false;
                        return;  
                }
                Point p = this.DataGridView1.GetCellDisplayRectangle(e.ColumnIndex, e.RowIndex, false).Location;
                this.ComboBox1.Location = p;
                this.ComboBox1.Size = this.DataGridView1.GetCellDisplayRectangle(e.ColumnIndex, e.RowIndex, false).Size;
                this.ComboBox1.Visible = true;
            }
            else
            ...{
                this.ComboBox1.Visible = false;
            } 
        }
       private void ComboBox1_TextChanged(object sender, EventArgs e)
        ...{
            this.DataGridView1.CurrentCell.Value = this.ComboBox1.Text;
        }