How do you use CsvHelper to write a class derived from DynamicObject?

Question

How do you use CsvHelper to write a class derived from DynamicObject?

I was hoping to use a dynamically typed object to write to a CSV file.

I am getting "CsvHelper.CsvWriterException" in the CsvWriter.WriteObject method with this message: "No properties are displayed for type" WpmExport.DynamicEntry ".

Here is the class I'm trying to use:

public class DynamicEntry : DynamicObject
{
    private Dictionary<string, object> dictionary = new Dictionary<string, object>();

    public override bool TryGetMember(
        GetMemberBinder binder, out object result)
    {
        string name = binder.Name.ToLower();
        return dictionary.TryGetValue(name, out result);
    }

    public override bool TrySetMember(
        SetMemberBinder binder, object value)
    {
        dictionary[binder.Name.ToLower()] = value;
        return true;
    }

    public override IEnumerable<string> GetDynamicMemberNames()
    {
        return dictionary.Keys.AsEnumerable();
    }
}

Anyone with ideas or working examples? The documentation at http://joshclose.github.io/CsvHelper/ suggests that this is possible, but does not provide any guidance.

TIA

+3

c # .net dynamic csvhelper

Mitch baker 27 Sep '14 at 6:46

source to share

2 answers

Josh Close · Answer 1 · 2014-10-01T21:26:13+0000

The functionality doesn't exist yet. You can write dynamic

, but not DynamicObject

. You can see a thread on this topic. https://github.com/JoshClose/CsvHelper/issues/187

When the functionality is implemented, I will update the answer to the version it is in.

Update

This functionality will be available in version 3.0. You can try the 3.0 beta from NuGet.

FaustsErbe · Answer 2 · 2016-11-17T16:31:59+0000

Since I can't wait for version 3.0 (and CsvHelper.Excel to support it), I found an intermediate solution.

Got a class for export:

public partial class EntryReportInventory
{
    public Guid DeviceId { get; set; }
    [ReportProperty]
    public string DeviceName { get; set; }

    public Dictionary<string, object> InventoryValues { get; set; }

    public EntryReportInventory(Device device, Dictionary<string, object> inventoryValues)
    {
        this.DeviceId = device.Id;
        this.DeviceName = device.Name;

        this.InventoryValues = inventoryValues;
    }
}

Created cartographer:

Type genericClass = typeof(DefaultCsvClassMap<>);
Type constructedClass = genericClass.MakeGenericType(typeof(EntryReportInventory));
                return (CsvClassMap)Activator.CreateInstance(constructedClass);

And now the magic. I am iterating over all properties.

foreach (PropertyInfo property in mapping)
            {
...
if (isInventoryReportBaseType && typeof(Dictionary<string, object>).IsAssignableFrom(property.PropertyType))
                {
                    var dataSource = (ReportInventoryBase)Activator.CreateInstance(entityType, dbContext);

                    foreach (var item in dataSource.ColumnNameAndText)
                    {
                        var columnName = item.Key;

                        var newMap = new CsvPropertyMap(property);
                        newMap.Name(columnName);
                        newMap.TypeConverter(new InventoryEntryListSpecifiedTypeConverter(item.Key));

                        customMap.PropertyMaps.Add(newMap);
                    }
...
}

And my converter:

    public class InventoryEntryListSpecifiedTypeConverter : CsvHelper.TypeConversion.ITypeConverter
    {
        private string indexKey;
        public InventoryEntryListSpecifiedTypeConverter(string indexKey)
        {
            this.indexKey = indexKey;
        }

        public bool CanConvertFrom(Type type)
        {
            return true;
        }

        public bool CanConvertTo(Type type)
        {
            return true;
        }

        public object ConvertFromString(TypeConverterOptions options, string text)
        {
            throw new NotImplementedException();
        }

        public string ConvertToString(TypeConverterOptions options, object value)
        {
            var myValue = value as Dictionary<string, object>;
            if (value == null || myValue.Count == 0) return null;

            return myValue[indexKey] + "";
        }
    }

Not sure why, but it works to pass the same property multiple times. This :) You only need to have a list before (here: dataSource.ColumnNameAndText populated from an external source) to identify the columns / values.

How do you use CsvHelper to write a class derived from DynamicObject?

More articles: