关于C#.NET用户登录验证的详细代码

protected void btn_ok_Click(object sender, EventArgs e)
{
string conn;
string users, pwd;
users = username.Text;
pwd = userpwd.Text;
SqlConnection conn = new SqlConnection("server=localhost;database=test;uid=;pwd=;");
SqlConnection con = SqlConnection(Sql, conn);
con.Open();
SqlCommand dr = new SqlCommand("select count(*) as icount from test where username="+users+"");
}

这是我写的一部分代码，现在就是我不那个count怎么使用和怎样判断用户名和密码数据库中是否存在、对不对。代码要详细，

protected void btn_ok_Click(object sender, EventArgs e)
{
string conn;
string users, pwd;
users = username.Text;
pwd = userpwd.Text;
SqlConnection conn = new SqlConnection("server=localhost;database=test;uid=;pwd=;");
SqlConnection con = SqlConnection(Sql, conn);
con.Open();
SqlCommand dr = new SqlCommand("select count(*) as icount from test where username="+users+"");
SqlDataAdapter sda=new SqlDataAdapter(dr);
DataTable dt=new DataTable();
sda.Fill(dt);
con.Close();
if(dt.Rows.Count>=1)
{
Response.Redirect("跳转页面");
}
else
{
Response.Write("不存在的用户名");
}

}

string conn,users,pwd; users=username.text; pwd = userpwd.Text; SqlConnection conn = new SqlConnection("server=localhost;database=test;uid=;pwd=;"); SqlConnection con = SqlConnection(Sql, conn); con.Open(); SqlCommand dr = new SqlCommand("select * from test where username="+users+""); SqlCommand dr1 = new SqlCommand("select * from test where username="+users+""and password="+pwd+" ); Data.SqlClient.SqlDataReader myreader = dr.ExecuteReader; Data.SqlClient.SqlDataReader myreader1 = dr1.ExecuteReader; if myreader.read() then if myreader1.read() then '登陆 else '密码错误 endif else '没有该用户 endif

select username,password from test where username="+users+" and password="+pwd+" 然后执行并查看结果行数，要是一行都没有就是密码不正确了

是这样的，count(*)是数据返回的行数，如果你输入的用户名和密码存在，则count返回的数字应该为1，如果不存在则为0（数据库中不存在该用户），所以if(count(*)!=0){则数据库存在该用户}else{用户不存在} string sql=string.format("select count(*) from test where username={0}and pwd={1}", username.Text,userpwd.Text);注：username为数据库表中用户的用户名，pwd为密码都是表中的字段名

select count(*) from test where username="'+users+'" and pwd = "'+pwd+'" 然后 cmd.Connection = conn; int flag =Convert.ToInt32(dr.ExcuteScalar()); if(flag>0) { //登陆成功逻辑 } else { //登陆失败逻辑 }