Delegate assignable as a class property to be called within a class

Victor

I'm wondering if it is possible to allow a developer to write a function in aspx codebehind, place the name of the function in a custom WebControl's property, and have that function be called within said WebControl.

The problem I'm trying to solve is this: I have a custom GridView that allows the user to page, sort, search and make changes to data from a database table without committing the changes to the data to the table until the user clicks a "Save" button. I bind my custom gridview to a databaseobject. That databaseobject accesses select and update methods that are defined by my custom business logic objects, which in turn access datasets I created using the dataset wizards.

I solved the issue of caching the changes by adding an object to record the changes and saving/loading that object to/from viewstate.

The issue I'm running into is matching the changed values to the rows that the changed values apply to. I can't use RowIndex because the RowIndex indexes the currently visible rows, and as the user pages the gridview the rowindex will change which row/dataitem it actually points to. Originally I used DataItemIndex, but if the user changes the search parameters and thus changes the underlying dataset, the datasex index is reset and so the old dataitemindex does not apply any more.

So what I am trying now is matching based off the DataKeys. I can access the DataKeys within my custom gridview, and I'm trying to search through my custom object that stores the changes to find a matching set of keys, but the problem I'm running into now is that a DataKey stores the value as type "object" and I can't get a match by comparing two values as objects. I need to cast the objects first before comparing, but inside my custom gridview I have no idea what type those objects, the value of each datakey, will be. They could be ints, strings, etc.

So I figured I would allow the user to define that process of comparison outside my custom gridview in the aspx codebehind itself and then tell the gridview to call that function when its time to match the DataKeys of the row to the datakeys of my custom "changes" object.

Is this possible?

Any suggestions of a better way to go about doing this?

3 Replies

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Nilanka Dharmadasa16y ago
Accepted answer
Hi Victor,

Yes. it is possible with delegates.

If I understood your problem correctly, this solution will help you.

I wrote a dummy sample for you. Check it. I haven't written the method bodies. But you can get the idea from it. An you can write the method bodies.

If you find this answer helpful, please tick 'Do you like this answer' checkbox.
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Victor16y ago
TheLizard, thanks for the suggestion. That would probably work but I want to avoid having to use and maintain a switch statement to handle all possible cases.

niki d, thanks, your example helped to get my understanding started.
I put a delegate in my class and made it public so that it could be assigned in the codebehind.
I ran into a problem where I could not save to view state (serialize) the object because of the delegate, so I moved the data to a seperate object (List) within my class and just serialized that instead of the whole class. I define my delegate in code behind, assign it to my custom control and I can now match the object with the changed values to the rows that the changed values apply to.
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theLizard16y ago
I am not entirely sure about what you want to do but if you are having problems regarding casting of objects based on object type in the grid view ( I am assuming these are fields from the table!) then you could have a class which has the field definitions for the dataset you have loaded into the grid and cast the objects based on the session objects fieldType

class members would be something like;

fieldName;
fieldIndex;
datatype;

blah blah.

the session object would be a List or
an array of fieldDefClass[] whatever

when the need to compare values you can do a switch on field type eg;

switch(sessionObject.FeildType)
   {
   case "varchar")
      string s = session.object.value;
changed = (s == changedValue? true : false);

let me know if i am on the right track to help you!
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