CustomModelMetadataProvider

public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(IEnumerable<Attribute> attributes, Type containerType, Func<object> modelAccessor, Type modelType, string propertyName)
    {
        var attributeList = attributes.ToList();
        var modelMetadata = base.CreateMetadata(attributeList, containerType, modelAccessor, modelType, propertyName);

        ProvideTextAreaForBigText(modelMetadata, propertyName);

        return modelMetadata;
    }

    private void ProvideTextAreaForBigText(ModelMetadata modelMetadata, string propertyName)
    {
        if (propertyName != null && propertyName.EndsWith("_BigText") && string.IsNullOrEmpty(modelMetadata.TemplateHint))
            modelMetadata.TemplateHint = "BigText";
    }
}