How do I get dapper to map an int to a boolean property
Question
I have this class...
public class MyDTO
{
public int Id { get; set; }
public bool Selected { get; set; }
}
and then use dapper to attempt to create a list like this...
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 });
which returns a result set like this....
id selected
9 0
10 1
11 1
12 0
But when code above is executed, i get an error
[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
I'm going to create a "Translating" property for now, but is this an unusual use case?
Solution
I'm not sure if this is the best way to do it, but it should do the trick:
SELECT T1.id, CAST(CASE WHEN T2.id IS NULL THEN 0 ELSE 1 END AS BIT) AS selected
FROM ...
(To be honest, I'm not convinced that your T2.id IS NOT NULL AS selected
clause is legal T-SQL in the first place, but if you say that it's working then I'll take your word for it!)
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