equals in c# is true

Question

I am doing webmethod in c#. On debugging,

(chk.Equals(oldpass))

the query shows same value on both left and right side.

But still,instead of going inside if,execution moves to else part showing return statement. Foll. is my code.

[WebMethod (Description="for change in password")]
public string update(string authenid,string oldpass,string newpass)
{
     SqlConnection conn = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=D:\\Workspace\\visual studio workspace\\Tmrepo\\App_Data\\tmrepo.mdf;Integrated Security=True;User Instance=True");

    try
    {
        conn.Open();

  string chk = "select pwd from client where authenid = '"+ @authenid +"' ";
        if(chk.Equals(oldpass))
        {
            string update = "update client set pwd=@newpass where pwd=@oldpass and authenid=@authenid";
            SqlCommand cmd = new SqlCommand(update, conn);
            cmd.Connection = conn;
            cmd.Parameters.AddWithValue("@authenid", authenid);
            cmd.Parameters.AddWithValue("@oldpass", oldpass);
            cmd.Parameters.AddWithValue("@newpass", newpass);
            cmd.ExecuteNonQuery();

        }

        else
        {
            return "invalid oldpass";
        }
 conn.Close();
        return newpass;
    }
    catch (Exception ex)
    {
        return ex.ToString();
    }

}

Is anything wrong in this code? I am ac# newbie. Thanks.

Answer 1

You haven't executed the command: your old password chk is: "select pwd from client where authenid = '"+ @authenid +"' ";, which is an unlikely password. Look into ExecuteScalar, for example.

Additional thoughts:

• parameterize the sql - don't concatenate the id in; it should be "select pwd from client where authenid = @authenid"; where you are adding a parameter named authenid with the value from authenid . You get this right in the second ADO.NET query.
• passwords should be salted and hashed: not stored directly; you should never be able to extract and/or decrypt a password

---

(external edits)

Update : Execute code as "select pwd from client where authenid = '"+ @authenid +"' "; because "select pwd from client where authenid = '@authenid' "; returns null value.

update2 : cmd.ExecuteScalar(); made it work. And remove cmd.ExecuteNonQuery();

Answer 2

what your code doing is comparing select pwd from client where authenid = some_value against the value of oldpass, which will be false!

Fixed Code Logic :

        string oldpass = "somehing";

        string authenid = "pass_to_test";
        string sql = string.Format("select pwd from client where authenid = '{0}' ", authenid);
        string chk = null;
        SqlCommand cmd = new SqlCommand(update, conn);

        var reader = cmd.ExecuteReader();
        if (reader.Read())
        {
            // has record with username
            chk = reader.GetString(0);
            if (chk.Equals(oldpass))
            {
                string update = "update client set pwd=@newpass where pwd=@oldpass and authenid=@authenid";

                cmd.CommandText = update;
                cmd.Connection = conn;
                cmd.Parameters.AddWithValue("@authenid", authenid);
                cmd.Parameters.AddWithValue("@oldpass", oldpass);
                cmd.Parameters.AddWithValue("@newpass", newpass);
                cmd.ExecuteNonQuery();

            }

            else
            {
                return "invalid oldpass";
            }

        }
        else
        {
            // not a valid username
        }
        reader.Close();
        reader.Dispose();

Answer 3

Finally,solved!!! I used dataset. The second method with perfectly correct code is :

string chk = "select pwd from client where authenid = @authenid";
        SqlCommand cmd1 = new SqlCommand(chk , conn);
        cmd1.Parameters.AddWithValue("@authenid", authenid);
        DataSet ds = new DataSet();
        SqlDataAdapter da = new SqlDataAdapter(cmd1);
        da.Fill(ds);
        int cnt = ds.Tables[0].Rows.Count;
        if (cnt > 0)
        {
            if (ds.Tables[0].Rows[0]["pwd"].ToString().Equals(oldpass))
            {
                string update = "update client set pwd=@newpass where pwd=@oldpass and authenid=@authenid";
                SqlCommand cmd = new SqlCommand(update, conn);
                cmd.Connection = conn;
                cmd.Parameters.AddWithValue("@authenid", authenid);
                cmd.Parameters.AddWithValue("@oldpass", oldpass);
                cmd.Parameters.AddWithValue("@newpass", newpass);
                cmd.ExecuteNonQuery();
            }            
        }

Hope it helps other newbies like me!!