_connection.Open(); //_connection это переменная SqlConnection
            SqlCommand LoadCategories = new SqlCommand();
            LoadCategories.CommandText = "exec LoadCategories";
            LoadCategories.Connection = _connection;
 
            SqlDataReader reader = LoadCategories.ExecuteReader();
 
            while (reader.Read())
            {
                Categories.Add(
                    new Category()
                    {
                        Id = Convert.ToInt32(reader["Id"]), //Тут в кавычках название столбца из таблицы в базе
                        Name = reader["Name"].ToString() //Если берешь значение varchar то лучше юзать ToString() или аналог из Convert
                    }
                    );
            }
            _connection.Close();

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