Question

I have a class like this:

public class LocalizedDataAnnotationsModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(IEnumerable<Attribute> attributes, Type containerType,
                                                    Func<object> modelAccessor, Type modelType, string propertyName)
    {
        var meta = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);
        if (string.IsNullOrWhiteSpace(propertyName))
            return meta;
        if (meta.DisplayName == null)
            GetLocalizedDisplayName(meta, propertyName);
        if (string.IsNullOrWhiteSpace(meta.DisplayName))
        {
            string resource = string.Format("{0}_{1}", meta.ContainerType.Name, meta.PropertyName).ToLower();
            meta.DisplayName = string.Format("[{0}]", resource);
        }
        return meta;
    }

    private static void GetLocalizedDisplayName(ModelMetadata meta, string propertyName)
    {
        ResourceManager rm = new ResourceManager(typeof (i18n));
        CultureInfo culture = Thread.CurrentThread.CurrentUICulture;
        string resource = string.Format("{0}_{1}", meta.ContainerType.Name, meta.PropertyName).ToLower();
        meta.DisplayName = rm.GetString(resource, culture);
    }
}

I want to abstract away the line

ResourceManager rm = new ResourceManager(typeof (i18n));

I want to make this class indenpendent of the type i18n. I want to be able to specify the type for the resource manager at construction/initialization, making the class more universal and put it in a standalone class library.

What are my options? Can it be done with a static class or do I have to have non-static class? Or can I just leave the way it is, abstract the rm as class field and initialize it in the constructor?

Thank you

UPDATE: Please note the class will most likely be used in various ASP.NET MVC sites in global.asax.cs like this:

protected override void OnApplicationStarted()
{
    base.OnApplicationStarted();
    ModelMetadataProviders.Current = new LocalizedDataAnnotationsModelMetadataProvider();
}

I am never actually referencing or using this class directly, ASP.NET MVC does everything under the hood.

Answer 1

You can make the class generic:

    public class LocalizedDataAnnotationsModelMetadataProvider<T> : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(IEnumerable<Attribute> attributes, Type containerType,
                                                    Func<object> modelAccessor, Type modelType, string propertyName)
    {
        var meta = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);
        if (string.IsNullOrWhiteSpace(propertyName))
            return meta;
        if (meta.DisplayName == null)
            GetLocalizedDisplayName<T>(meta, propertyName);
        if (string.IsNullOrWhiteSpace(meta.DisplayName))
        {
            string resource = string.Format("{0}_{1}", meta.ContainerType.Name, meta.PropertyName).ToLower();
            meta.DisplayName = string.Format("[{0}]", resource);
        }
        return meta;
    }

    private static void GetLocalizedDisplayName<T>(ModelMetadata meta, string propertyName)
    {
        ResourceManager rm = new ResourceManager(typeof (T));
        CultureInfo culture = Thread.CurrentThread.CurrentUICulture;
        string resource = string.Format("{0}_{1}", meta.ContainerType.Name, meta.PropertyName).ToLower();
        meta.DisplayName = rm.GetString(resource, culture);
    }

And set it up like this:

ModelMetadataProviders.Current = new LocalizedDataAnnotationsModelMetadataProvider<i18n>();