问题
In using Dapper's Query() function, I am trying to fill in a class that has a property which is an enumerated value. In my database, this column is stored as a byte. However, in the class, they are an enum. In the old ADO.NET approach, I'd convert during the reader loop:
myClass.myEnum = (MyEnumType) reader.GetByte(2);
When using Dapper, I can't figure out how to do this conversion. For example when I do something like
myClass = conn.Query<MyClassType>("SELECT ... ")
I get an error of the type
Error parsing column 2 (myEnum=1 - Byte)
Is there a way to use Dapper's Query() to fill in a class that contains properties which are enum types?
回答1:
Sure - as long as your enum agrees, i.e.
enum MyEnumType : byte {
Foo, Bar, Blip, ...
}
then it will all work automatically.
(this limitation is by design, and shared with LINQ-to-SQL as it happens)
Alternatively, if the enum is : int and can't be changed, cast it in the SQL:
SELECT ..., CAST(x.myEnum as int) as myEnum, ...
Or finally, use the dynamic API:
foreach(var row in conn.Query(...)) { // note no <T>
T obj = new Item { /* copy from row */ };
...
}
The first is my preferred object, as that enforces the byte data-type limitation throughout all your code, which is IMO a good thing.
来源：https://stackoverflow.com/questions/6086216/using-dapper-to-populate-enum-properties