Dapper and Data Type Conversions.

Question

Hi Friends. I was wondering whats the most efficient way to convert from one Data Type to another while working with Dapper Objects. I keep getting this compile error Cannot implicitly convert type Datapacketpayer[]to DatapackePayerPayee[]. Thanks !!!

Answer 1

Usually with Dapper two classes (and in your case I may get this wrong as I not sure how the relations are setup in the database) the query uses a join, then for Dapper see spliton.

Example

I have a contact model and a ContactDevices model, to get data the SELECT statement. In my case I created the models using a tool.

SELECT C.ContactId,
       C.FirstName,
       C.LastName,
       C.ContactTypeIdentifier,
       CT.ContactTitle,
       CD.id AS DeviceId,
       CD.ContactId,
       CD.PhoneTypeIdentifier,
       CD.PhoneNumber,
       CT.ContactTypeIdentifier
FROM dbo.Contacts AS C
    INNER JOIN dbo.ContactType AS CT
        ON C.ContactTypeIdentifier = CT.ContactTypeIdentifier
    INNER JOIN dbo.ContactDevices AS CD
        ON C.ContactId = CD.ContactId;;

Then in code (SQL.ContactsWithDevices points to the statement above) we get each contact with one or more contact devices. My code is a tad more complex e.g. there is more to contact devices e.g. types of devices and locations.

public static async Task<List<Contacts>> GetContactsAndDevices()
{
    await using SqlConnection cn = new(ConnectionString());

    var list = cn.Query<Contacts, ContactDevices, Contacts>(
        SQL.ContactsWithDevices(), (contact,  contactDevices) =>
        {

            contact.ContactDevices.Add(contactDevices);
            return contact;
        }, splitOn: "ContactId,DeviceId");


    return list.ToList();
}