database1.mdf內容結構如下：

id  char(10) primary key

username char(10)

userpass char(10)

內容：

id     username      userpass

1                  1                  1

2                  2                  2

database2.mdf內容結構如下：

id  char(10) primary key

username char(10)

userpass char(10)

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

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string Conn = @"Data Source=.\SQLEXPRESS;AttachDbFilename='C:\Users\lenovo\AppData\Local\Temporary Projects\WindowsFormsApplication1\Database1.mdf';Integrated Security=True;User Instance=True";
            SqlConnection conn = new SqlConnection(Conn);
            string sSql = "select * from Table1";
            SqlDataAdapter da = new SqlDataAdapter(sSql, conn);
            DataSet ds = new DataSet();
            da.Fill(ds);
            //MessageBox.Show(ds.Tables[0].Rows[1][2].ToString());
            for (int i = 0; i < ds.Tables[0].Rows.Count; i++) {
                fun(ds.Tables[0].Rows[i][0].ToString(), ds.Tables[0].Rows[i][1].ToString(), ds.Tables[0].Rows[i][2].ToString());
            }
            dataGridView1.DataSource = ds.Tables[0];  
        }
        public void fun(string s1, string s2, string s3)
        {

            SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename='C:\Users\lenovo\AppData\Local\Temporary Projects\WindowsFormsApplication1\Database2.mdf';Integrated Security=True;User Instance=True");
            StringBuilder strSQL = new StringBuilder();//建立StringBuilder物件

            strSQL.Append("insert into Table2 values('"+s1+"','"+s2+"','"+s3+"')");
            using (SqlCommand cmd =//建立資料庫命令物件
                new SqlCommand(strSQL.ToString(), con))
            {
                con.Open();//開啟資料庫連線
                cmd.ExecuteNonQuery();//執行SQL命令
                MessageBox.Show("新增資料成功");//彈出訊息對話方塊
                con.Close();//關閉資料庫連線
            }

        }


    }
}