Reflective Code

What follows is a generic class for generating CSV files.

Usage

    CsvWriter<MyObject> writer = new CsvWriter<MyObject>();
    writer.Header = true;
    writer.AddColumn("Id", x => x.Id.ToString());
    writer.AddColumn("Name", x => x.Name);
    writer.AddColumn("Price", x => x.Price.ToString());
    writer.AddColumn("Guid", x => x.Guid);
    writer.AddColumn("Description", x => x.Description);
    writer.AddColumn("Url", x => x.Url);

    IEnumerable<MyObject> objects = Load();
    string csv = writer.WriteToString(objects);
    File.WriteAllText("objects.csv", csv);

Classes

    class CsvWriter<T>
    {
        private readonly List<CsvColumn<T>> _columns = new List<CsvColumn<T>>();

        public bool Header { get; set; }
        public bool QuoteAll { get; set; }
        public IEnumerable<CsvColumn<T>> Columns { get { return _columns; } }

        public void AddColumn(string name, Func<T, string> value)
        {
            if (name == null) throw new ArgumentNullException("name");
            if (value == null) throw new ArgumentNullException("value");

            foreach (CsvColumn<T> column in _columns)
                if (column.Name == name)
                    throw new Exception("Column with same name already added.");

            _columns.Add(new CsvColumn<T>(name, value));
        }

        public string WriteToString(IEnumerable<T> items)
        {
            if (items == null) throw new ArgumentNullException("items");

            StringWriter writer = new StringWriter();
            WriteToStream(writer, items);
            return writer.ToString();
        }

        public void WriteToStream(TextWriter stream, IEnumerable<T> items)
        {
            if (stream == null) throw new ArgumentNullException("stream");
            if (items == null) throw new ArgumentNullException("items");

            if (Header)
                WriteHeader(stream);

            foreach (T item in items)
                WriteRow(stream, item);
        }

        private void WriteHeader(TextWriter stream)
        {
            bool first = true;
            foreach (CsvColumn<T> column in _columns)
            {
                if (first)
                    first = false;
                else
                    stream.Write(',');

                WriteValue(stream, column.Name);
            }
            stream.Write('\n');
        }

        private void WriteRow(TextWriter stream, T item)
        {
            if (item == null) return;

            bool first = true;
            foreach (CsvColumn<T> column in _columns)
            {
                if (first)
                    first = false;
                else
                    stream.Write(',');

                WriteValue(stream, column.Value(item));
            }
            stream.Write('\n');
        }

        private void WriteValue(TextWriter stream, string value)
        {
            if (value == null) return;

            if (QuoteAll || ContainsAny(value, '\"', ',', '\x0A', '\x0D'))
            {
                stream.Write("\"");
                stream.Write(value.Replace("\"", "\"\""));
                stream.Write("\"");
            }
            else
            {
                stream.Write(value);
            }
        }

        private static bool ContainsAny(string value, params char[] characters)
        {
            return value.IndexOfAny(characters) != -1;
        }
    }

    class CsvColumn<T>
    {
        public string Name { get; private set; }
        public Func<T, string> Value { get; private set; }

        public CsvColumn(string name, Func<T, string> value)
        {
            if (name == null) throw new ArgumentNullException("name");
            if (value == null) throw new ArgumentNullException("value");

            Name = name;
            Value = value;
        }
    }

I wanted to print the contents of some objects, for debugging purposes. One option was to override my Class’s ToString method and simply use Console.WriteLine(myObject). I do this on a few classes, and suddenly I have to maintain all these ToString methods whenever I change their properties or fields.

All that extra work, just for some debug statements? I think not – I’d rather the computer do the work for me. After all, it always knows what properties my objects have. So I wrote a method for automatically generating a “pretty” snapshot of an object’s state. C# code follows.

Console.WriteLine(AutoString(DBNull.Value));
// DBNull { }

Console.WriteLine(AutoString("A String", true));
// String
// {
//   FirstChar:      A
//   Length:         8
//   m_firstChar:    A
//   m_stringLength: 8
// }

Console.WriteLine(AutoString(new Customer
{
    Id = 12,
    Name = "Smith",
    Address = new Address
    {
        City = "Springfield"
    }
}));
// Customer
// {
//   Address: TestApp.Address
//   Id:      12
//   Name:    Smith
//   Region:
// }

public static string AutoString(object obj, bool includeNonPublic = false)
{
    if (obj == null) return "null";

    Type type = obj.GetType();

    BindingFlags flags = BindingFlags.Instance | BindingFlags.Public;
    if (includeNonPublic)
        flags = flags | BindingFlags.NonPublic;

    List<MemberInfo> members = type.GetProperties(flags)
                                    .Where(property => property.GetIndexParameters().Length == 0)
                                    .Cast<MemberInfo>()
                                    .Concat(type.GetFields(flags))
                                    .OrderBy(member => member.Name)
                                    .ToList();

    StringBuilder sb = new StringBuilder();

    if (members.Count > 0)
    {
        sb.AppendLine(type.Name);
        sb.AppendLine("{");

        int longest = members.Max(m => m.Name.Length);
        foreach (MemberInfo member in members)
        {
            sb.Append("  ");
            sb.Append(member.Name);
            sb.Append(":");
            sb.Append(' ', longest - member.Name.Length + 1);
            sb.Append(GetValue(member as PropertyInfo, obj));
            sb.Append(GetValue(member as FieldInfo, obj));
            sb.AppendLine();
        }

        sb.Append("}");
    }
    else
    {
        sb.Append(type.Name);
        sb.Append(" { }");
    }

    return sb.ToString();
}

private static string GetValue(PropertyInfo property, object instance)
{
    if (property == null) return null;
    var value = property.GetValue(instance, null);
    if (value == null) return null;
    return value.ToString();
}

private static string GetValue(FieldInfo field, object instance)
{
    if (field == null) return null;
    var value = field.GetValue(instance);
    if (value == null) return null;
    return value.ToString();
}