数据库操作

string strcon = @"Data Source=.;Initial Catalog=XSXX;Integrated Security=True";
//Data Source=数据库  Initial Catalog=目录

添加操作：

using (SqlConnection con=new SqlConnection(strcon))   //连接数据库
{

     　　 string sql = "INSERT INTO XS VALUES('" + user + "','" + pwd + "')"; //数据库指令  XS:表名称  
　　　　　　//INSERT INTO XS VALUES('张山','123456');

         using (SqlCommand cmd=new SqlCommand(sql,con))
         { 
               con.Open();      //打开数据库
               cmd.ExecuteNonQuery();//执行命令

         }
  }

删除操作：

int r = dataGridView1.SelectedRows.Count;  //要删除的行数
if (r != 0)
{
    int index = dataGridView1.CurrentRow.Index;  //获取该行的位置
    string s = dataGridView1.Rows[index].Cells[0].Value.ToString(); //第一个字段的内容
    using (SqlConnection con = new SqlConnection(strcon))
    {
        string sql = "delete from " + Table + " where 账号='" + s + "'";   
        //delete from XS where name='张三'  删除指令
        using (SqlCommand cmd = new SqlCommand(sql, con))
             {
                  con.Open();
                  cmd.ExecuteNonQuery();
                        
              }
                  
     }
}

修改：

 using (SqlConnection con = new SqlConnection(strcon))
 {
       string sql = "update " + Taable + " set 密码='" + s + "' where 账号='" + user + "'";
       // update XS set 密码='654321' where 账号='张三'
       using (SqlCommand cmd = new SqlCommand(sql, con))
       {
            con.Open();
            cmd.ExecuteNonQuery();
                      
       }
                  
  }

查询：

using (SqlConnection sqlcon = new SqlConnection(strcon))
{
   sqlcon.Open();
   string sql = "SELECT * FROM " + Taable + " where 账号='" + content + "'";
　　//SELECT * FROM XS where 账号='张三'；
   SqlCommand cmd = new SqlCommand(sql, sqlcon);
   SqlDataAdapter myda = new SqlDataAdapter(cmd);
   myst.Tables.Clear(); //Dataset myst=new Dataset();
   myda.Fill(myst, "" + Taable + "");
   dataGridView1.DataSource = myst.Tables["" + Taable + ""];
}