为什么这段代码在一个解决方案中编译而不在另一个解决方案中编译？ [关闭]

Question

我在一个解决方案中有此代码，它工作正常：

        private readonly List<Department> departments = new List<Department>();

        . . .

        private void LoadDepartments(string serialNum)
        {
            string dbContext = HandheldServerUtils.GetDBContextForSerialNum(serialNum);
            string connStr =
                string.Format(
                    @"Provider=Microsoft.ACE.OLEDB.12.0;User ID=NRBQSP;Password=NRBQSP;Data Source=C:\CCRWin\DATA\CCRDAT{0}.MDB;Jet OLEDB:System database=C:\CCRWin\Data\sscs.mdw",
                    dbContext);
            using (var conn = new OleDbConnection(connStr))
            {
                using (OleDbCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText =
                        @"SELECT t_accounts.account_no as AccountID, IIF(ISNULL(t_accounts.name),'[blank]',t_accounts.name) AS Name 
                        FROM t_accounts 
                        INNER JOIN td_department_accounts ON (t_accounts.account_no = 
td_department_accounts.account_no) where type = 'DE'";
                    cmd.CommandType = CommandType.Text;
                    conn.Open();
                    int i = 1;
                    using (OleDbDataReader oleDbD8aReader = cmd.ExecuteReader())
                    {
                        while (oleDbD8aReader != null && oleDbD8aReader.Read())
                        {
                            string accountNum = oleDbD8aReader.GetString(0);
                            string deptName = oleDbD8aReader.GetString(1);
                            Add(new Department {Id = i, AccountId = accountNum, Name = deptName});
                            i++;
                        }
                    }
                }
            }
        }

我在另一个代码中有非常相似的代码：

    public IEnumerable<Department> GetDepartments()
    {
        private readonly List<Department> departments = new List<Department>();
        string dbContext = "42"; 
        string connStr =
            string.Format(
                @"Provider=Microsoft.ACE.OLEDB.12.0;User ID=NRBQSP;Password=NRBQSP;Data Source=C:\CCRWin\DATA\CCRDAT{0}.MDB;Jet OLEDB:System database=C:\CCRWin\Data\sscs.mdw",
                dbContext);
        using (var conn = new OleDbConnection(connStr))
        {
            using (OleDbCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText =
                    @"SELECT t_accounts.account_no as AccountID, IIF(ISNULL(t_accounts.name),'[blank]',t_accounts.name) AS Name 
                    FROM t_accounts 
                    INNER JOIN td_department_accounts ON (t_accounts.account_no = td_department_accounts.account_no) where type = 'DE'";
                cmd.CommandType = CommandType.Text;
                conn.Open();
                int i = 1;
                using (OleDbDataReader oleDbD8aReader = cmd.ExecuteReader())
                {
                    while (oleDbD8aReader != null && oleDbD8aReader.Read())
                    {
                        string accountNum = oleDbD8aReader.GetString(0);
                        string deptName = oleDbD8aReader.GetString(1);
                        departments.Add(new Department { Id = i, AccountId = oleDbD8aReader.GetInt16(0), Name = oleDbD8aReader.GetString(1) });
                        i++;
                    }
                }                    
            }
        }
        return departments;
    }

...它咳出 26 个错误，例如：

"；预期"

在这条线和其他线上：

using (var conn = new OleDbConnection(connStr))

-and "} expected" 就在开头的 "{"

--and “命名空间不能直接包含字段或方法等成员”

在这一行：

departments.Add(new Department { Id = i, AccountId = oleDbD8aReader.GetInt16(0), Name = oleDbD8aReader.GetString(1) });

-以及“类、结构或接口成员声明中的无效标记 '!='”：

while (oleDbD8aReader != null && oleDbD8aReader.Read())

...以及“（”和“，”和“;”和“{”和“=”和“使用”的许多其他“无效令牌”错误

-和两个“类型或命名空间定义，或预期的文件结尾”

如果我注释掉除 return 语句之外的所有代码，那么它就是：

public IEnumerable<Department> GetDepartments()
{
    return null;
}

...它编译得很好。

为什么这里对鹅好对鹅不好？

Answer 1

这一行……​​

private readonly List<Department> departments = new List<Department>();

... 不应在函数中，而应在类范围之外，或者将其设为 var。