ADO.NET :: Finding Lambda Expression Against Entity Framework Collection?
Aug 6, 2010
I'm new to LINQ and EF and I seem to be having trouble working this out.
I have a many-to-many relationship between my Location and Region tables. When adding or editing a Location, my interface allows the user to check any number of related Regions. If they click OK, I need to add any new relationships that were checked, and delete any existing relationships that have been unchecked. My basic code is shown below.
However, this code doesn't work. Lower down, the line location.Regions.Contains(region) returns false even when the location already is related to the region. The issue appears to be because the region is from my populated listbox that was initialized earlier and is no longer part of the current EF context. But if I try and add it, I get an error that there is already a Region with that ID.
It seems like what I want to do is change this line to something like location.Regions.Contains((r) => r.RgnID == region.RgnID) so I'm only testing for a particular ID. But this gives me the error "Cannot convert lambda expression to type 'TrailCalendar.Region' because it is not a delegate type."
I don't understand this error but, either way, I'm not sure how I can test if the relationship already exists without reloading a bunch of data, which I'd like to avoid.
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[code]....
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[Code]....
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[Code]....
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[Code]....
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