悬崖上的金鱼片尾曲:这段c#+sqlserver的登陆代码哪里不对?

SqlConnection conn=new SqlConnection("Server=purana;Database=test;Integrated Security=SSPI");
SqlCommand cmd=new SqlCommand();
cmd.CommandText="Select * From user_info where user_name=@name";
cmd.Connection=conn;
cmd.Parameters.Add(new SqlParameter("@name",SqlDbType.VarChar,20));
cmd.Parameters["@name"].Value=textBox1.Text;
SqlDataAdapter ada=new SqlDataAdapter(cmd);
DataSet ds=new DataSet();
conn.Open();
ada.Fill(ds,"user_info");
DataTable dt=ds.Tables[0];
if(dt.Rows.Count>0)
{

if(dt.Rows[0]["user_password"].ToString().Trim()==textBox2.Text)
MessageBox.Show("登录成功");
else
MessageBox.Show("密码错误");
}
else
MessageBox.Show("没有此用户");
conn.Close();