I have an Encounter type and a Response that inherits it:
[BsonKnownTypes(typeof(Request), typeof(Response))]
public abstract class Encounter {
public ObjectId Id { get; set; }
}
// .. some more Encounter subtypes ...
public class Response : Encounter {
public bool IsResponded;
}
I want to be able to pass an Encounter or a subtype of it to the Db.UpdateEncounterAsync() method:
class Db {
private IMongoCollection<Encounter> EncounersCollection;
// ... stuff ...
public Db() {
EncounersCollection = InitCollection();
}
// ... stuff ...
public async Task UpdateEncounterAsync<TEncounter, TField>(
TEncounter encounter, Expression<Func<TEncounter, TField>> fieldFuncExpr)
where TEncounter : Encounter
{
var value = fieldFuncExpr.Compile()(encounter);
var updateDefinition = Builders<Encounter>.Update
.Set(fieldFuncExpr, value); // Error CS1503
var updateResult = await EncounersCollection.UpdateOneAsync(
e => e.Id == encounter.Id, updateDefinition);
}
}
In the following way:
Response response = GetResponse();
response.IsResponded = true;
// update just the IsResponded field of the response object:
UpdateEncounterAsync(response, r => r.IsResponded);
But my UpdateEncounterAsync doesn't compile:
Error CS1503 Argument 1: cannot convert from 'System.Linq.Expressions.Expression<System.Func<TEncounter, TField>>' to 'MongoDB.Driver.FieldDefinition<DataModel.Encounter, TField>'
That's because fieldFuncExpr is of type Expression<Func<TEncounter, TField>>, where TEncounter : Encounter, but Builders<Encounter>.Update.Set(expr, value) expects expr of type Expression<Func<Encounter, TField>> and not the generic TEncounter.
Is there an elegant way around it?
