Generic conversion function doesn't seem to work with Guids

Question

I have the following code:

public static T ParameterFetchValue<T>(string parameterKey)
{
    Parameter result = null;

    result = ParameterRepository.FetchParameter(parameterKey);

    return (T)Convert.ChangeType(result.CurrentValue, typeof(T), CultureInfo.InvariantCulture);  
}

The type of result.CurrentValue is string. I would like to be able to convert it to Guid but I keep getting the error:

Invalid cast from System.String to System.Guid

This works perfectly with primitive data types.
Is there any way to make this work for non-primitive data types?

Answer 1

How about:

T t = (T)TypeDescriptor.GetConverter(typeof(T)).ConvertFromInvariantString(text);

Works fine for Guid and most other types.

Answer 2

Try This:

public object ChangeType(object value, Type type)
    {
        if (value == null && type.IsGenericType) return Activator.CreateInstance(type);
        if (value == null) return null;
        if (type == value.GetType()) return value;
        if (type.IsEnum)
        {
            if (value is string)
                return Enum.Parse(type, value as string);
            else
                return Enum.ToObject(type, value);
        }
        if (!type.IsInterface && type.IsGenericType)
        {
            Type innerType = type.GetGenericArguments()[0];
            object innerValue = ChangeType(value, innerType);
            return Activator.CreateInstance(type, new object[] { innerValue });
        }
        if (value is string && type == typeof(Guid)) return new Guid(value as string);
        if (value is string && type == typeof(Version)) return new Version(value as string);
        if (!(value is IConvertible)) return value;
        return Convert.ChangeType(value, type);
    }