Relative and absolute URIs have different restrictions on their format. For example, a relative URI does not require a scheme or an authority. The value you specify in uriKind must match the type of URI passed in uriString. However, if RelativeOrAbsolute is specified, the URI string can be relative or absolute.
The uriString can be poorly formed and can still be used to construct a Uri instance. The Windows Phone runtime will try to correct some minor issues with a poorly-formed string when this constructor is called to create a Uri instance.
This constructor does not ensure that the Uri refers to an accessible resource.