CODEWITHSUNDEEP
stringlinqlist
user1740172
user1740172

Reputation: 21

What is wrong in this LINQ Query, getting compile error

I have a list AllIDs:

List<IAddress> AllIDs = new List<IAddress>();

I want to do substring operation on a member field AddressId based on a character "_".

I am using below LINQ query but getting compilation error:

AllIDs= AllIDs.Where(s => s.AddressId.Length >= s.AddressId.IndexOf("_"))
    .Select(s => s.AddressId.Substring(s.AddressId.IndexOf("_")))
    .ToList();

Error:

Cannot implicitly convert type 'System.Collections.Generic.List<string>' to 'System.Collections.Generic.List<MyCompany.Common.Users.IAddress>'

Upvotes: 2

Views: 92

Answers (3)

Wasp
Wasp

Reputation: 3425

Maybe this?

var boundable  = 
    from s id in AllIDs
    where s.AddressId.Length >= s.AddressId.IndexOf("_")
    select new { AddressId = s.AddressId.Substring(s.AddressId.IndexOf("_")) };
boundable = boundable.ToList();

Upvotes: 0

Matthew Kennedy
Matthew Kennedy

Reputation: 616

If you want to put them back into Address objects (assuming you have an Address class in addition to your IAddress interface), you can do something like this (assuming the constructor for Address is in place):

AllIDs = AllIDs.Where(...).Select(new Address(s.AddressID.Substring(s.AddressID.IndexOf("_")))).ToList();

You should also look at using query syntax for LINQ instead of method syntax, it can clean up and improve the readability of a lot of queries like this. Your original (unmodified) query is roughly equivalent to this:

var substrings = from a in AllIDs
                 let id = a.AddressId
                 let idx = id.IndexOf("_")
                 where id.Length >= idx
                 select id.Substring(idx);

Though this is really just a style thing, and this compiles to the same thing as the original. One slight difference is that you only have to call String.IndexOf() one per entry, instead of twice per entry. let is your friend.

Upvotes: 0

lc.
lc.

Reputation: 116438

AllIDs is a list of IAddress but you are selecting a string. The compiler is complaining it cannot convert a List<string> to a List<IAddress>. Did you mean the following instead?

var substrings = AllIDs.Where(...).Select(...).ToList();

Upvotes: 3

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