c# how to implement type converter

Question

I am struggling to implement a simple Type converter in C#. I followed this guide https://msdn.microsoft.com/en-us/library/ayybcxe5.aspx

Here is my class :

Answer 1

The code provided is a bit mixed up and it's missing some important stuff. Following, an implementation that converts a custom class CrazyClass from and to string.

CrazyClassTypeConverter

public class CrazyClassTypeConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
        return sourceType == typeof(string) || base.CanConvertFrom(context, sourceType);
    }

    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        var casted = value as string;
        return casted != null
            ? new CrazyClass(casted.ToCharArray())
            : base.ConvertFrom(context, culture, value);
    }
    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
    {
        var casted = value as CrazyClass;
        return destinationType == typeof (string) && casted != null
            ? String.Join("", casted.Charray)
            : base.ConvertTo(context, culture, value, destinationType);
    }
}

CrazyClass

(note that the class is decorated with TypeConverterAttribute)

[TypeConverter(typeof(CrazyClassTypeConverter))]
public class CrazyClass
{
    public char[] Charray { get; }

    public CrazyClass(char[] charray)
    {
        Charray = charray;
    }
}

Usage

var crazyClass = new CrazyClass(new [] {'T', 'e', 's', 't'});
var converter = TypeDescriptor.GetConverter(typeof(CrazyClass));

//this should provide you the string "Test"        
var crazyClassToString = converter.ConvertToString(crazyClass); 

//provides you an instance of CrazyClass with property Charray set to {'W', 'h', 'a', 't' } 
var stringToCrazyClass = converter.ConvertFrom("What"); 

Answer 2

You have to attach this converter to a class with the TypeConverter attribute.
TypeDescriptor.GetConverter Get the attached converter of the class.

You better split the classes:

[TypeConverter(typeof (TestClassConverter))]
public class TestClass
{
    public string Property1 { get; set; }
    public int Property2 { get; set; }
    public TestClass(string p1, int p2)
    {
        Property1 = p1;
        Property2 = p2;
    }
}

[TypeConverter(typeof (TestClassConverter))]
public class TestClassConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context,
    Type sourceType)
    {
        if (sourceType == typeof(string))
        {
            return true;
        }
        return base.CanConvertFrom(context, sourceType);
    }
    public override object ConvertFrom(ITypeDescriptorContext context,
     CultureInfo culture, object value)
    {
        if (value is string)
        {
            return new TestClass("", Int32.Parse(value.ToString()));
        }
        return base.ConvertFrom(context, culture, value);
    }
    public override object ConvertTo(ITypeDescriptorContext context,
    CultureInfo culture, object value, Type destinationType)
    {
        if (destinationType == typeof(string)) { return "___"; }
        return base.ConvertTo(context, culture, value, destinationType);
    }
}