.net - 如何让 dapper 将 int 映射到 bool 属性

Question

我有这个课...

public class MyDTO
{
    public int Id { get; set; }

    public bool Selected { get; set; }
}

然后使用 dapper 尝试创建这样的列表......

            var list = this.db.OpenConnection().Query<MyDTO>(
            @"SELECT T1.id, T2.id IS NOT NULL AS selected
            FROM     table1 T1
            LEFT
            JOIN     table2 T2 
            ON   T2.id = T1.id
            AND  Tl.id = @Id",
            new { Id = id });

它返回这样的结果集....

id  selected
 9         0
10         1
11         1
12         0

但是当上面的代码被执行时，我得到一个错误

[InvalidCastException: Specified cast is not valid.]
Deserialize3d3c9260-abcb-4964-97c1-4a4e66b786d3(IDataReader ) +354

[DataException: Error parsing column 2 (selected=0 - Int64)]
Dapper.SqlMapper.ThrowDataException(Exception ex, Int32 index, IDataReader reader) in     C:\Projects\Web\SqlMapper.cs:1685
Deserialize3d3c9260-abcb-4964-97c1-4a4e66b786d3(IDataReader ) +432
Dapper.<QueryInternal>d__13`1.MoveNext() in C:\Projects\Web\Source\SqlMapper.cs:608
System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +327
System.Linq.Enumerable.ToList(IEnumerable`1 source) +58
Dapper.SqlMapper.Query(IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable`1 commandTimeout, Nullable`1 commandType) in C:\Projects\Web\Source\SqlMapper.cs:538

我现在要创建一个“翻译”属性，但这是一个不寻常的用例吗？

Answer 1

我不确定这是否是最好的方法，但它应该可以解决问题:

SELECT T1.id, CAST(CASE WHEN T2.id IS NULL THEN 0 ELSE 1 END AS BIT) AS selected
FROM ...

(老实说，我不相信你的 T2.id IS NOT NULL AS selected 子句首先是合法的 T-SQL，但如果你说它有效，那么我会相信你的话!)