做一个密码验证登陆！连接的是access数据库！有usernam和password  2个textbox还有一个登入button！在access数据库里面已经写好用户名和密码！怎么才能通过button_chick事件判断输入的usernam和passwo是不是在数据库里面的呢！是则通过，否则返回！忘指教下！

找个例子，看看就会了

    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void btnLogin_Click(object sender, EventArgs e)
    {
        SqlConnection objConnection = new SqlConnection(strConnet);
        SqlCommand objCommand = new SqlCommand("", objConnection);
         = "SELECT USERID,NICKNAME,USERROLE FROM USERS WHERE USERNAME=@NAME AND USERPASSWORD=@PASSWORD";
        objCommand.Parameters.Add("NAME",SqlDbType.VarChar);
        objCommand.Parameters.Add("PASSWORD", SqlDbType.VarChar);
        objCommand.Parameters["NAME"].Value = tbxName.Text.Trim();
        objCommand.Parameters["PASSWORD"].Value = tbxPassword.Text.Trim();
        try
        {
            if (objConnection.State == ConnectionState.Closed)
            {
                objConnection.Open();
            }
            SqlDataReader result = objCommand.ExecuteReader();
            if (result.Read() == true)
            {
                Session["USERID"] = result["USERID"].ToString();
                Session["NICKNAME"] = result["NICKNAME"].ToString();
                Session["USERROLE"] = result["USERRILE"].ToString();
                if (Session["USERROLE"].ToString() == "1")
                {
                    Response.Redirect("Manager.aspx");
                }
                else
                {
                    Response.Redirect("Welcom.aspx");
                }
            }
            else
            {
                labError.Visible = true;
            }
        }
上面是我写的一个登录模块的 垃圾代码  用的是SQL
仿照着写 access数据库大概就这个样子

private void button1_Click(object sender, EventArgs e)//登录按钮
        {
            if (textBox1.Text.Trim () == ""||textBox2.Text.Trim () == "")
            {
                MessageBox.Show("对不起，你还没有输入用户名和密码", "提示");
                textBox3.Focus();
            }
            else
            {
                    OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=数据库名称");
                    conn.Open();
                    OleDbDataAdapter dauser = new OleDbDataAdapter("Select * from usermessage where username='" + textBox1.Text.Trim() + "'", conn);
                    DataSet dsuser = new DataSet();
                    dauser.Fill(dsuser, "usermessage");
                    if (dsuser.Tables[0].Rows.Count == 0)//判断用户是否存在
                    //用户不存在，给出提示后清空文本框再定位光标到文本框1
                    {
                        MessageBox.Show("对不起，您还没有注册，请先注册", "提示");
                        textBox1.Clear();
                        textBox2.Clear();
                        textBox1.Focus();
                    }
                    else
                    //用户存在，再判断密码是否正确
                    {
                        DataRow[] dr = dsuser.Tables[0].Select("username='" + textBox1.Text + "'");//为取数据表中某列字段内容做准备
                        if ((dr[0]["userpassword"].ToString(), textBox2.Text) == 0)//判断密码是否相等到
                        //密码也正确，则显示登录成功窗体
                        {
                MessageBox.Show("成功", "提示");//也可以写你需要做的事情
                        }
                        else
                            //密码不正确，给出提示，再定位光标重输密码
                        {
                            MessageBox.Show("对不起，密码错误，请重新输入", "提示");
                            textBox2.Clear();
                            textBox2.Focus();
                        }

                    }
                }
               
            }

private void button1_Click(object sender, EventArgs e)//登录按钮
        {
            if (textBox1.Text.Trim () == ""||textBox2.Text.Trim () == "")
            {
                MessageBox.Show("对不起，你还没有输入用户名和密码", "提示");
                textBox3.Focus();
            }
            else
            {
                    OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=数据库名称");
                    conn.Open();
                    OleDbDataAdapter dauser = new OleDbDataAdapter("Select * from usermessage where username='" + textBox1.Text.Trim() + "'", conn);
                    DataSet dsuser = new DataSet();
                    dauser.Fill(dsuser, "usermessage");
                    if (dsuser.Tables[0].Rows.Count == 0)//判断用户是否存在
                    //用户不存在，给出提示后清空文本框再定位光标到文本框1
                    {
                        MessageBox.Show("对不起，您还没有注册，请先注册", "提示");
                        textBox1.Clear();
                        textBox2.Clear();
                        textBox1.Focus();
                    }
                    else
                    //用户存在，再判断密码是否正确
                    {
                        DataRow[] dr = dsuser.Tables[0].Select("username='" + textBox1.Text + "'");//为取数据表中某列字段内容做准备
                        if ((dr[0]["userpassword"].ToString(), textBox2.Text) == 0)//判断密码是否相等到
                        //密码也正确，则显示登录成功窗体
                        {
                MessageBox.Show("成功", "提示");//也可以写你需要做的事情
                        }
                        else
                            //密码不正确，给出提示，再定位光标重输密码
                        {
                            MessageBox.Show("对不起，密码错误，请重新输入", "提示");
                            textBox2.Clear();
                            textBox2.Focus();
                        }

                    }
                }
               
            }