Question

我有一个SQLite表＆＃34;短语＆＃34;像：

CREATE TABLE [phrases] (
[id] INTEGER PRIMARY KEY AUTOINCREMENT, 
[phrase] CHAR, 
[parent_id] INTEGER);

我用演示数据填充它：

id  | phrase         | parent_id
1   | parent phrase  | (null)
2   | some child 1   | 1
3   | some child 2   | 1

我有一个C＃模型，如：

class Phrase
{
    int id { get; set; }
    string phrase { get; set; }
    int parent_id { get; set; }
    Phrase parent { get; set; }
}

如何正确使用Dapper将此表映射到此类？感谢。

Answer 1

您需要在选择查询中添加短语child（我使用MS-SQL）：

SELECT      p.id        AS id,
            p.phrase    AS phrase,
            p.parent_id AS parent_id,
            c.id        AS id,
            c.phrase    AS phrase
FROM        phrases p
LEFT JOIN   phrases c ON p.id = c.parent_id

Dapper能够通过假设您的Id列被命名为Id或id（默认情况下）来拆分返回的行。

C＃：

public IEnumerable<Phrase> GetPhrase()
    {
        const string sql = @"   SELECT      p.id        AS id,
                                            p.phrase    AS phrase,
                                            p.parent_id AS parent_id,
                                            c.id        AS id,
                                            c.phrase    AS phrase
                                FROM        phrases p
                                LEFT JOIN   phrases c ON p.id = c.parent_id";

        using (var connection = OpenConnection(_connectionString))
        {
            return connection.Query<Phrase, Phrase, Phrase>(sql, (p, c) =>
            {
                p.parent = c;

                return p;
            }, commandType: CommandType.Text);
        }
    }

此作品仅适用于一个级别的子级到父级（不适用于嵌套式）

由parent_id进行的Dapper Multi Mapping

1 个答案: