Storing TimeSpan with Entity Framework Codefirst - SqlDbType.Time overflow

Now EF Core actually has built-in ticks <=> TimeSpan conversion. All you have to do is:

builder.Property(p => p.SomeTimeSpanProperty)
    .HasConversion<long>();

No need to instantiate a new TimeSpanToTicksConverter or anything. Just specify the type long as the generic argument, and you're done.

For more info see EF Core Built-in Value Converters

In this line:

Span = new TimeSpan(1, 0, 0, 0)

You're using this constructor:

public TimeSpan(int days, int hours, int minutes, int seconds);

So you're actually creating a TimeSpan greater than 24 hours since you're passing 1 to the days parameter, while your underlying Database type is Time which only accepts values between 00:00-23:59.

Hard to tell whether you actually meant to have a TimeSpan with 1 day, or it's just a typo.

If you really want a TimeSpan greater than 24 hours, i guess you'll have to map your field to another Database type (like SmallDateTime).

If it's just a typo error, just change your line to:

Span = new TimeSpan(1, 0, 0),

    [Browsable(false)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    [Obsolete("Property '" + nameof(Duration) + "' should be used instead.")]        
    public long DurationTicks { get; set; }

    [NotMapped]
    public TimeSpan Duration
    {
#pragma warning disable 618
      get { return new TimeSpan(DurationTicks); }
      set { DurationTicks = value.Ticks; }
#pragma warning restore 618
    }

Update

This is now achievable since EF Core 2.1, using Value Conversion.

builder.Entity<Stage>()
    .Property(s => s.Span)
    .HasConversion(new TimeSpanToTicksConverter()); // or TimeSpanToStringConverter

Doing a time-to-ticks conversion on both ends is no longer silly. Not sure when they added it, but Entity Framework will now select the appropriate built in converter if one exists (in this case TimeSpanToTicksConverter). All you need to do is add a single attribute to your entity class and Entity Framework will automagically give the column in the SQL table the same range as the TimeSpan class.

public class Stage
{
    public string Name { get; set; }

    [Column(TypeName = "bigint")]
    public TimeSpan Span { get; set; }

    public int StageId { get; set; }
}

I'm sure bigint isn't the default column type for TimeSpan for human readability and backwards compatibility, but this seems like a pretty much perfect solution.

I hope this helps anybody experiencing this issue six years later.

Documentation: https://docs.microsoft.com/en-us/ef/core/modeling/value-conversions