C#: Export a List of Objects to CSV with LINQ, Attributes, and Generics

/// <summary>
/// The name of the column for the CSV
/// generated by a list of objects with
/// properties marked with this attribute,
/// if Export is true.  Uses Order to order
/// the properties on export
/// </summary>
public class CsvColumnNameAttribute : Attribute
{
    public bool Export { get; set; }
    public int Order { get; set; }
    public string Name { get; set; }

    public CsvColumnNameAttribute()
    {
        Export = true;
        Order = int.MaxValue; // so unordered columns are at the end
    }

}

public class MyClassToExport
{
    [CsvColumnAttribute(Name = "Activation Date", Order = 1)]  
    public DateTime Date { get; set; }
   
    [CsvColumnAttribute(Name = "Full Name", Order = 2)]
    public string User { get; set; }
   
    [CsvColumnAttribute(Name = "Account Type", Order = 3)]
    public int Level { get; set; }
   
    [CsvColumnAttribute(Name = "Account Action", Order = 4)]
    public string Action { get; set; }
   
    [CsvColumnAttribute(Export = false)]
    public DateTime Added { get; set; }
}

/// <summary>
/// Generate a CSV as a string from a list
/// of objects that have the CsvColumnNameAttribute
/// applied
/// </summary>
public string GetCsv<T>(List<T> csvDataObjects)
{
    PropertyInfo[] propertyInfos = typeof(T).GetProperties();
    var sb = new StringBuilder();
    sb.AppendLine(GetCsvHeaderSorted(propertyInfos));
    csvDataObjects.ForEach(d => sb.AppendLine(GetCsvDataRowSorted(d, propertyInfos)));
    return sb.ToString();
}

private string GetCsvDataRowSorted<T>(T csvDataObject, PropertyInfo[] propertyInfos)
{
    IEnumerable<string> valuesSorted = propertyInfos
        .Select(x => new
        {
            Value = x.GetValue(csvDataObject, null),
            Attribute = (CsvColumnNameAttribute)Attribute.GetCustomAttribute(x, typeof(CsvColumnNameAttribute), false)
        })
        .Where(x => x.Attribute != null && x.Attribute.Export)
        .OrderBy(x => x.Attribute.Order)
        .Select(x => GetPropertyValueAsString(x.Value));
    return String.Join(",", valuesSorted);
}

private string GetCsvHeaderSorted(PropertyInfo[] propertyInfos)
{
    IEnumerable<string> headersSorted = propertyInfos
        .Select(x => (CsvColumnNameAttribute)Attribute.GetCustomAttribute(x, typeof(CsvColumnNameAttribute), false))
        .Where(x => x != null && x.Export)
        .OrderBy(x => x.Order)
        .Select(x => x.Name);
    return String.Join(",", headersSorted);
}

private string GetPropertyValueAsString(object propertyValue)
{
    string propertyValueString;

    if (propertyValue == null)
        propertyValueString = "";
    else if (propertyValue is DateTime)
        propertyValueString = ((DateTime)propertyValue).ToString("dd MMM yyyy");
    else if (propertyValue is int)
        propertyValueString = propertyValue.ToString();
    else if (propertyValue is float)
        propertyValueString = ((float)propertyValue).ToString("#.####"); // format as you need it
    else if (propertyValue is double)
        propertyValueString = ((double)propertyValue).ToString("#.####"); // format as you need it
    else // treat as a string
        propertyValueString = @"""" + propertyValue.ToString().Replace(@"""", @"""""") + @""""; // quotes with 2 quotes

    return propertyValueString;
}

// example usage
var export = new List<MyClassToExport>();
// TODO add items to list :)
var csv = GetCsv(export);