Problem object service parameter

Question

Hi,

in the startup.cs module of a Blazor server project I declared this endpoint:

            endpoints.MapPost("/timestamp/addtimestamp/", (context) =>
            {
                var timestamp = context.Request.ReadFromJsonAsync<Timestamp>();
                (Timestamp ReturnTimestamp, var error) = app.ApplicationServices.GetService<TimestampService>().AddTimestamp(timestamp);
                var json = JsonSerializer.Serialize(new { ReturnTimestamp = ReturnTimestamp, error = error });
                return context.Response.WriteAsync(json);
            });

the AddTimestamp service should receive a TimeStamp object as "parameter":

public (Timestamp, Error) AddTimestamp(Timestamp timestamp)
{
...
}

I get this error:
Error CS1503 Argument 1: cannot convert from 'System.Threading.Tasks.ValueTask<TSNet.BO.Timestamp?>' to 'TSNet.BO.Timestamp'

the "timestamp" object, that is passed as a parameter to AddTimestamp servize, is not Timestamp obejct

How can I "convert" it?

Best
Stefano

Answer 1

you should learn about c# types and nullability.

ReadFromJson can return a null (no content), so it return Nullable<Timestamp>. This means you must cast the return value to non-null to pass as a value type rather than a nullable object.

            (Timestamp ReturnTimestamp, var error) = app.ApplicationServices.GetService<TimestampService>().AddTimestamp((Timestamp) timestamp);