How to lookup and invoke a .Net TypeConverter for a particular type?

Question

I would like to implement a general purpose runtime type conversion function that makes use .Net TypeConverters to do the conversion.

Does anyone know how to how t

Answer 1

Here's the code used in one of our existing apps... not sure if it's ideal but it works well for us.

/// 

/// Attempts to convert a value using any customer TypeConverters applied to the member
/// 
/// Object containing the value to be assigned
/// Member to be assigned to
///  converted to the appropriate type
public static Object CustomTypeConversion ( object value, MemberInfo member )
{
    if ( value == null || value == DBNull.Value )
        return value;

    if ( member == null )
        throw new ArgumentNullException ( );

    List converters = GetCustomTypeConverters ( member );

    foreach ( TypeConverter c in converters )
    {
        if ( c.CanConvertFrom ( value.GetType ( ) ) )
            return c.ConvertFrom ( value );
    }

    if ( member is PropertyInfo )
    {
        PropertyInfo prop = member as PropertyInfo;
        return ConvertToNative( value , prop.PropertyType );
    }
    return ConvertToNative ( value, member.MemberType.GetType ( ) );
}

/// 

/// Extracts and instantiates any customer type converters assigned to a 
/// derivitive of the  property
/// 
/// Any class deriving from MemberInfo
/// A list of customer type converters, empty if none found
public static List GetCustomTypeConverters ( System.Reflection.MemberInfo member )
{
    List result = new List();

    try
    {
        foreach ( TypeConverterAttribute a in member.GetCustomAttributes( typeof( TypeConverterAttribute ) , true ) )
        {
            TypeConverter converter = Activator.CreateInstance( Type.GetType( a.ConverterTypeName ) ) as TypeConverter;

            if ( converter != null )
                result.Add( converter );
        }
    }
    catch
    {
        // Let it go, there were no custom converters
    }

    return result;
}

/// 

/// Attempts to cast the incoming database field to the property type
/// 
/// Database value to cast
/// Type to cast to
/// The converted value, if conversion failed the original value will be returned
public static object ConvertToNative ( object value , Type castTo )
{
    try
    {
        return Convert.ChangeType( value , castTo , System.Threading.Thread.CurrentThread.CurrentCulture );
    }
    catch
    {
        return value;
    }
}

Just call the CustomTypeConversion method and away you go... probably a little more than you need but being thorough isn't a crime (or is it?).