value-converter.md

BakingSheet Value Converter

BakingSheet supports ValueConverter to support custom data type.

Note that ValueConverter will be only used when you importing or exporting with cell-based converters (Excel, Google Sheet, CSV).

You can extend JsonSheetConverter instead, if you want to specify converting logic and configuration when you converting to JSON.

Defining Sheet Value Converter

To support custom data type, user can implement own SheetValueConverter for the type.

For example, this is built-in DateTime converter.

public class DateTimeValueConverter : SheetValueConverter<DateTime>
{
    protected override DateTime StringToValue(Type type, string value, SheetValueConvertingContext context)
    {
        var local = DateTime.Parse(value, context.FormatProvider);
        return TimeZoneInfo.ConvertTimeToUtc(local, context.TimeZoneInfo);
    }

    protected override string ValueToString(Type type, DateTime value, SheetValueConvertingContext context)
    {
        var local = TimeZoneInfo.ConvertTimeFromUtc(value, context.TimeZoneInfo);
        return local.ToString(context.FormatProvider);
    }
}

Specifying Converter with Attribute

You can specify your custom SheetValueConverter with SheetValueConverterAttribute.

You can specify on specific Type,

[SheetValueConverter(typeof(MyTypeConverter))]
public class MyType
{
    // ...
}

Or specify on specific column.

public class MySheet : Sheet<MySheet.Row>
{
    public class Row : SheetRow
    {
        [SheetValueConverter(typeof(MyColumnConverter))]
        public int MyColumn { get; set; }
    }
}

Specifying Converter with ContractResolver

And you can specify your custom ValueConverter by overriding SheetContainerBase.ContractResolver.

public class MySheetContainer : SheetContainerBase
{
    // sheet definitions
    public ItemSheet Items { get; set; }
    public CharacterSheet Characters { get; set; }
    
    // constructor
    public MySheetContainer(ILogger logger) : base(logger) { }
    
    // overrides
    public readonly static SheetContractResolver ContractResolverInstace = new SheetContractResolver(new MyValueConverter());
    
    public override SheetContractResolver ContractResolver => ContractResolverInstace;
}

It is advised to reuse SheetContractResolver instance, since it will contain reflection information for value converters.