Vault of Thoughts

2006-08-01

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Strongly Typed Templated Controls

All of us who have been using any kind of ASP.NET Templated Controls such as FormView, sooner or later come to a problem of extracting value from a field inside a template. For example when you are using a FormView control and want to programatically access a control inside one of the templates. What are the options? You have to resort to some kind of FindControl calls which are way from perfect. I have been thinking about this issue for some time now and I have an idea.


The idea is to change tha way the PageBuildProvider constructs the part of class that represents the ASPX file of your page. (the other one is of course the code behind). So what could be changed? Imagine a situation where you have a page and there is just one FormView on it. The FormView has its templates defined in an ASPX file. What happens now is the ASP.NET framework builds the part of the class given this ASPX file and what we get is a nice intellisense in the code behind telling us that the our class has a field FormView1 of type FormView which of course does not have any knowledge about controls inside the templates. But what if...


But what if instead of the FormView1 being of type FormView, the part of the class constructed from ASPX file provided us with a field FormView1 of type derived from the FormView but with few additional properties which represent controls found inside the templates - in a strongly typed manner.


Now. The benefits of such a solution are obvious mainly compile time type checking.


Is it possible to make ASP.NET 2.0 to provide such a solution? This is a hard question. I have checked the major components that are responsible for the way the classes are constructed now. I haven't gone deep into details but it it looks like some changes inside the PageBuildProvider (or some base classes) would be required. Also a ControlBuilder responsible for building a templated control would have to constuct a whole new class representing our control. I suppose that the major problem lies in constructing such a derived class with all those properties representing inner controls.


So basically I hope MS will/is thinking about making our lives easier and more type safe :-) or maybe some brave developer is willing to try to implement my concept? Either way it would be nice to have such a feature some time in the future.


Some additional considerations include the problem with accessing controls from ItemTemplate of a FormView control when in Edit mode. Another issou would be with controls such as GridView where some of the templates represent a repeating content and not a single data etc...


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