C# Code is not properly catching errors.

Code
string hash(string s)

    {

        //hash it here    

        return s;

    }



    void btn()

    {

        //dont make a connection and other stuff if your textboxes are empty. Save resources, check for empty input FIRST

        if (string.IsNullOrWhiteSpace(emailTextbox.Text) || string.IsNullOrWhiteSpace(passwordTextbox.Text))

        {

            //display a message or so here.

            return;

        }



        //C# uses pascal casing, name your variables appropriately

        //trim the input to remove whitespaces etc.

        var inEmail = emailTextbox.Text.Trim();

        var inPass = passwordTextbox.Text.Trim();



        //hash the input password so we can compare it to the hashed passwords of the db.

        var hashedPass = hash(inPass);



        //using defines a block that will free up resources after the block has been run.

        //con gets cleaned this way

        var conStr = System.Configuration.ConfigurationManager.ConnectionStrings["SQLAzureConnection"].ConnectionString;



        var cmdString = $"SELECT TOP 1 * FROM Customer WHERE email = '{inEmail}' AND password = '{hashedPass}'";

        using (var con = new SqlConnection(conStr))

        using (var cmd = new SqlCommand(cmdString, con))

        {

            con.Open();

            using (var reader = cmd.ExecuteReader())

            {

                //read once.

                reader.Read();



                var emailFromDb = reader["email"].ToString();

                if (!string.IsNullOrWhiteSpace(emailFromDb))

                {

                    //the query went okay which means the pass is equal to that of the db.

                    //succes!

                    

                    //login user, show dialog, update 'last logged in' to db. etc!

                }

                else

                {

                    //show error that user/pass combo is incorrect.



                    //if you want seperate errors for email is wrong and pass is wrong,

                    //just only fetch the right email form db (if you cna do it the email is correct, else display error)

                    //then compare the hashes (if this is wrong the password is wrong)

                }



            }



        }

        //no need to close connection cause using is doing that for us

    }