Why does SqlCommand not pass parameter inside a HASHBYTES function?

I have a simple

code, which has a HASHBYTES function in it to retrieve data from my server.

using (var connection = new SqlConnection(connectionString))

{

    connection.Open();



    using (var command = new SqlCommand(commandString, connection))

    {

        command.Parameters.Add(new SqlParameter("mail", email));

        command.Parameters.Add(new SqlParameter("password", password));

        using (var reader = command.ExecuteReader())

        {

            while (reader.Read())

            {

                return true;

            }

            throw new InvalidDataException();

        }

    }

}

The commandString property looks like this:

DECLARE @pass varchar(50);

SET @pass = @password;



DECLARE @pwdHash varbinary(max);

SET @pwdHash = HASHBYTES('SHA2_256', @pass);



SELECT * FROM Users

WHERE email=@mail AND pwd=@pwdHash;

This code works, but why doesn't the shorter code below work?

In the case below, the function doesn't go inside the while loop and instead throws an exception.

DECLARE @pwdHash varbinary(max);

SET @pwdHash = HASHBYTES('SHA2_256', @password);



SELECT * FROM Users

WHERE email=@mail AND pwd=@pwdHash;

In both of these codes, the @password value is set as a , so it should work, right? Or am I missing something?