Type converter - Convert from string to type

Question

User712911596 posted

I have a custom type converter on a class that is working fine on the "ToString()". I have the reverse coded into the CanConvertFrom(), but I can't seem to find a way to create the object from a String. Am I missing something here?

Answer 1

User-252544907 posted

Simply override the ConvertFrom method on your TypeConverter class. So take its input string value, process it, and have the ConvertFrom method instantiate and return an instance of your class.

Hope that helps,
Wim

Answer 2

User712911596 posted

        public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value) {
            if (value == null) { return new Corner(); }

            if (value is String) {
                String[] vals = ((String)value).Split(' ');
                return new Corner(
                    (CornerSizes)Enum.Parse(typeof(CornerSizes), vals[0], true)
                    , (CornerTypes)Enum.Parse(typeof(CornerTypes), vals[1], true)
                );
            }

            return base.ConvertFrom(context, culture, value);
        }

 The above is defined in the Converter...I eventually found a way around my issue (by not doing the conversion at all), but I'm still interested in a answer.
 

Answer 3

User-252544907 posted

Can you show an example of the ToString() on your Corner object?

Thanks,
Wim

Answer 4

User712911596 posted

Sorry for the slow response...

        public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value) {
            if (value == null) { return new Corner(); }

            if (value is String) {
                String[] vals = ((String)value).Split(' ');
                return new Corner(
                    (CornerSizes)Enum.Parse(typeof(CornerSizes), vals[0], true)
                    , (CornerTypes)Enum.Parse(typeof(CornerTypes), vals[1], true)
                );
            }

            return base.ConvertFrom(context, culture, value);
        }

        public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType) {
            if (destinationType == typeof(String)) {
                Corner c = (Corner)value;
                return String.Format(
                    "{0} {1}"
                    , c.Size.ToString()
                    , c.Type.ToString()
                );
            }
            return base.ConvertTo(context, culture, value, destinationType);
        }

 

I couldn't find a way to call the ConvertFrom in my code, I was using the "defualt" ToString() method that is always available to get the Object to a string (and assuming it was using my logic in the ConvertTo() somehow). This is where I am confused.

Answer 5

User-252544907 posted

Darren,

If you want to explicitly call ConvertFrom on your typedescriptor, use the following:

Corner c = (Corner)TypeDescriptor.GetConverter(typeof(Corner)).ConvertFromString("30 solid");

That will subsequently call your overridden ConvertFrom method in your custom CornerTypeConverter class.

Does that help?

Cheers,
Wim