带参数的lightswitch查询

Question

I have a list where I select an item. Based on some field of this item i want to filter a choice list in another Control.

Somehing like that:

Select * from choiceItems Where choiceItem.ID = (Select ID from anotherTable where anotherTable.ID = selectedItem.ID)

the problem is that it is possible that there are more ID returns. Maybe I want all the choiceItems with the ID = {3,2,1} etc.

I cant preprocess the query on the server since my parameter is depending on the selected item in the list. If i try to filter the result in the query editor i can only specify on parameter which can be only a single value (fe ID=2).

How do i do that in silverlight?

Also, another unrelated small problem: Is it possible to show the waiting cursor while loading a custom control in lightswitch (right now it just displays a grey area until the data and controls are loaded).

Answer 1

Select * from choiceItems Where choiceItem.ID = (Select ID from anotherTable where anotherTable.ID = selectedItem.ID)

This is a many to many secenario, you need to make a WCF RIA Service with query parameter, a lot of work just for filtering. The alternative is to make those tables related.

Answer 2

You should be able to preprocess the query even if the parameter for the query is selected from a list. You can then use LINQ to return a subset of your choiceItems or, based on the selected parameter, skip the LINQ which would return all of the choiceItems .

I give a detailed example of doing this in my answer to the SO question:

Is there a way to create a search screen in Lightswitch based on a dropdown

Answer 3

Don't have the exact syntax, but should be something like this:

first get the ID using LINQ

var FilterOnThisId=this.Query1.Where(x=>x.ID==selectedItem.ID).FirstOrDefault();

then query the colleciton you want

var filtedItems=this.Query2.Where(x=>x.ID==FilterOnThisId);