SQLite+Dapper: Convert values to enum

Question

I have an SQLite database with an event table consisting of four columns: id (INT), timestamp (TEXT), level (TEXT) and message (TEXT). When I read back events, I want to convert the level values to corresponding LogLevel enum values. The text values are the same as the enum member names. How can I do this? I see that if I use Query<object> I get a list where I can enumerate through all rows and cast them before adding them to new Event struct values. But is this the best/easiest way to do this?

public struct Event
{
    public Event(DateTime timestamp, LogLevel level, string message)
    {
        Timestamp = timestamp;
        Level = level;
        Message = message;
    }
    public DateTime Timestamp { get; }
    public LogLevel Level { get; }
    public string Message { get; }
}

public enum LogLevel
{
    FATAL,
    ERROR,
    WARN,
    INFO
}

public List<Event> GetNewEvents(uint rowId)
{
    var events = _dbConnection.Query<Event>("SELECT * FROM events WHERE id >= @RowId;", new { RowId = rowId });
    return events.ToList();
}

Selçuk · Accepted Answer · 2018-01-15 18:24:52Z

2

Dapper will automatically map enum values if your 'level' column values matches with enum values. However you might have problem with that constructor. Also not sure why you have used struct. Just change your event to struct to class below.

public class Event
{           
    public DateTime Timestamp { get; set; }
    public LogLevel Level { get; set; }
    public string Message { get; set; }
}

Rest is the same.

answered Jan 15, 2018 at 18:24

Selçuk

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4 Comments

Oystein Over a year ago

I used a struct since I figured it was just a placeholder for values, which would never change when created. Actually, it doesn't seem to matter if I use a struct or a class. The problem was the constructor, as you pointed out.

Oystein Over a year ago

But that said, why should I use a class and not a struct in this case? Both works just the same, from what I see.

Selçuk Over a year ago

In your case there is no difference. Both will work fine. It's just rule of thumb.

Oystein Over a year ago

What is the rule of thumb? You're just telling me to change from struct to class, but not why.

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