dotnet/maui · error · NotImplementedException

Cannot convert "{dateTime}" into {destinationType}

Error message

Cannot convert "{dateTime}" into {destinationType}

What it means

ConvertToDestinationType(DateTime,...) throws NotImplementedException when destinationType is not string, DateTime, or DateOnly. Mirrors the DateOnly overload: only those three targets are accepted.

Source

Thrown at src/Controls/src/Core/DateTimeTypeConverter.cs:100

        throw new NotImplementedException($"Cannot convert \"{dateOnly}\" into {destinationType}");
    }

    static object ConvertToDestinationType(DateTime dateTime, Type? destinationType, CultureInfo? culture)
    {
        if (destinationType == typeof(string))
        {
            return dateTime.ToString(CultureInfo.InvariantCulture);
        }
        else if (destinationType == typeof(DateTime))
        {
            return dateTime;
        }
        else if (destinationType == typeof(DateOnly))
        {
            return DateOnly.FromDateTime(dateTime);
        }

        throw new NotImplementedException($"Cannot convert \"{dateTime}\" into {destinationType}");
    }
}

#endif

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Limit destinationType to string, DateTime, or DateOnly.
2. Convert to DateTime first, then transform to the final type yourself.

Example fix

// before
converter.ConvertTo(ctx, culture, DateTime.Now, typeof(long)); // ticks not supported

// after
var s = (string)converter.ConvertTo(ctx, culture, DateTime.Now, typeof(string));
var ticks = DateTime.Parse(s, CultureInfo.InvariantCulture).Ticks;

static bool SupportedDateTimeTarget(Type? t) =>
    t == typeof(string) || t == typeof(DateTime) || t == typeof(DateOnly);

static bool IsSupportedDestination(Type? t) => t is not null && (t == typeof(string) || t == typeof(DateTime) || t == typeof(DateOnly));

When it happens

Trigger: ConvertTo from a DateTime value to an unsupported destinationType such as InstanceDescriptor, DateTimeOffset, long (ticks), or a custom type.

Common situations: Designer/serialization requesting InstanceDescriptor; converting DateTime to a storage format the converter does not know.

Related errors

• Cannot convert "{value}" into {destinationType}
• Cannot convert "{dateOnly}" into {destinationType}
• Cannot convert "{value}" into {typeof(DateTime)}
• XC0004
• XC0040

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/5996effac43c2174. Report an issue: GitHub.