效果：

代碼：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace DataGridViewDownComboBoxDemo
{
    public partial class Form1 : Form
    {
        //級聯的列  
        DataGridViewComboBoxColumn columns3 = null
 
;
        public Form1()
        {
           
            InitializeComponent(); 
            this.dataGridView1.DataError += delegate (object sender, DataGridViewDataErrorEventArgs e) { };
        }
        /// <summary>  
        /// 綁定GRIDVIEW  
        /// </summary>  
        public void GetData()
        {
            
 
//第二列   
            DataGridViewComboBoxColumn columns2 = new DataGridViewComboBoxColumn();
            columns2.Name = "col2";
            columns2.DataPropertyName = "Type"; //從數據源綁定列，這一列就是那個值  
            columns2.HeaderText = "貨區";
            string[] strTmp = new string[] { "貨區A", "貨區B", "貨區C" , "
 
貨區D", "貨區E", "貨區F" };
            DgvCombobox(ref columns2, strTmp);//此方法是定義的關鍵   
            //第三列   
            columns3 = new DataGridViewComboBoxColumn();
            columns3.Name = "col3";
            columns3.HeaderText = "貨架";
            //生成gridview數據源  
            DataTable dt = new DataTable();
            dt.Columns.Add(new DataColumn("序號"));
            dt.Columns.Add(new DataColumn("物資名稱"));
            dt.Columns.Add(new DataColumn("物資編號"));
            for (int i = 0; i < 20; i++)
            {
                DataRow dr = dt.NewRow();
                dr[0] = i+1;
                dr[1] = "戴爾筆記本";
                dr[2] = "00000"+(i+1).ToString();
                dt.Rows.Add(dr);
            }
            this.dataGridView1.DataSource = dt;
            //gridview添加列  
            dataGridView1.Columns.AddRange(new DataGridViewColumn[] { columns2, columns3 });
        }
        /// <summary>  
        /// 綁定第二列  
        /// </summary>  
        /// <param name="column"></param>  
        /// <param name="strTmp"></param>  
        public void DgvCombobox(ref DataGridViewComboBoxColumn column, string[] strTmp)
        {
            DataTable dt = new DataTable();
            DataColumn dc = new DataColumn("tmp", typeof(string));
            dt.Columns.Add(dc);
            dt.Columns.Add(new DataColumn("ID", typeof(string)));
            DataRow dr;
            for (int i = 0; i < strTmp.Length; i++)
            {
                dr = dt.NewRow();
                dr["tmp"] = strTmp[i];
                dr["id"] = i;
                dt.Rows.Add(dr);
            }
            //為combobox綁定生成的表  
            column.DataSource = dt; //combobox列的數據源，綁定為生成的表  
            column.DisplayMember = "tmp";//要顯示的名稱，表的文字例  
            column.ValueMember = dt.Columns[1].ToString();//文字對應的值，此列將和columns2.DataPropertyName 屬性的值對應來顯示選中的值  

        }
        private void Form1_Load(object sender, EventArgs e)
        {
            this.GetData();
        }
        //添加委托事件  
        private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            if (this.dataGridView1.CurrentCell.OwningColumn.Name == "col2")
            {
                ((ComboBox)e.Control).SelectedIndexChanged +=
                                    new EventHandler(ComboBox_SelectedIndexChanged);
            }
        }

        private void ComboBox_SelectedIndexChanged(object sender, EventArgs e)
        { 
            if (this.dataGridView1.CurrentCell.OwningColumn.Name == "col2")
            { 
                     
                string str = ((ComboBox)sender).Text.ToString();
                //綁定第二個COMBOX  
                DataTable dt = new DataTable();
                dt.Columns.Add(new DataColumn("id"));
                dt.Columns.Add(new DataColumn("text"));

                for (int i = 0; i < 20; i++)
                {
                    DataRow dr = dt.NewRow();
                    dr[0] = str + i;
                    dr[1] = str + i;
                    dt.Rows.Add(dr);
                }
                ((DataGridViewComboBoxCell)this.dataGridView1.CurrentRow.Cells[4]).DataSource = dt;
                ((DataGridViewComboBoxCell)this.dataGridView1.CurrentRow.Cells[4]).DisplayMember = "text";
                ((DataGridViewComboBoxCell)this.dataGridView1.CurrentRow.Cells[4]).ValueMember = "id";
                ((ComboBox)sender).SelectedIndexChanged -= new EventHandler(ComboBox_SelectedIndexChanged);

            } 
        } 
    }
} 

提示：此demo不需要鏈接數據庫，只要在自己的窗體上創建一個datagridview命名為datagridview1即可。

C# DataGridView下DataGridViewComboBoxColumn二級聯動