design patterns - Is it okay to break LSP for the sake of binding? -

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something tells me might lynched asking this. , sorry long winded description in advance.

i'm working on of corner case in silverlight 4 project. i'm building custom form builder.

a form may have several fields may of different types (text, integer, email etc...). now, of these types extend field class might have additional properties length in case of text field.

i have ability add , remove fields collection of fieldviewmodels in formfieldsmanagementviewmodel. it's pretty standard stuff far.

now,... in order user set properties against field objects have usercontrol has dependency properties of type datatemplate , represent ui want dipsplay when particular type of field selected. , clarify, usercontrol has singlelinetexttemplate property shown when singlelinetextfieldviewmodel selected when emailfieldviewmodel selected, emailfieldtemplate shown. both singlelinetextfieldviewmodel , emailfieldviewmodel inherit fieldviewmodel.

my issue arises when declare bindings in each of these templates. it's quite valid (imho) set properties of base class fieldviewmodel isrequired , position have bindings length in singlelinetexttemplate match length property of singlelinetextfieldviewmodel. i'm relying on extended interface of concrete class rather fieldviewmodel class.

i should point out, before carry on this works. wasn't sure , does, i'm not sure should,..or should doing this.

i'm doing sake of binding , in absence of binding dynamic objects and/or lack of datatemplateselector in silverlight.

clearly, singlelinetextfieldviewmodel not substitutable it's base class in binding scenario. question is, since i'm not consuming these objects in code, in markup,..is still considered bad practice?

lots of in advance.

i wouldn't have problem - have done same or similar in past.

assuming use singlelinetexttemplate when datacontext instance of singlelinetextfieldviewmodel (presumably through mapping datatemplate type) there never problem, , because of resilient nature of binding framework not going have significant negative effects if try use template inappropriate type.


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