Help with Linq in VB.net

[Chinners]

Hi, I know this may not be the place to post this, but it is about syntax in VB, so I thought it would be the best place. (P.s. This is a VERY simplified example of what I want to do... I wouldnt waste effort with linq on something this simple :) ) I have a list of structures in VB, and can easily select an item from the list:

Public Structure UserInfo
Public ID As Integer
Public Name As String
End Structure

Dim Users As New List(Of UserInfo)

Users.Add(New UserInfo With {.ID = 1, .Name="Jim"})
Users.Add(New UserInfo With {.ID = 2, .Name="Bob"})
Users.Add(New UserInfo With {.ID = 3, .Name="Sue"})

Now, what I want to do is update user ID 3 (for example) to change the name from Sue to Susan... At the moment I use this:

  Dim User As UserInfo = (From UserInfo In Users Where UserInfo.ID = 3 Select UserInfo).First
  Users.Remove(User)
  User.Name = "Susan"
  Users.Add(User)

This works, but surely there is a better way? I have tried rooting through Google, but I am not sure of what I should be looking for to filter out all the Linq to sql and c# examples :confused: Please help!

[Guffa]

A structure should generally be immutable, and the point of using a structure is mostly defated as you have a reference type inside it. Use a class instead of a structure.

Public Class UserInfo
Public ID As Integer
Public Name As String
End Structure

Dim Users As New List(Of UserInfo)

Users.Add(New UserInfo With {.ID = 1, .Name="Jim"})
Users.Add(New UserInfo With {.ID = 2, .Name="Bob"})
Users.Add(New UserInfo With {.ID = 3, .Name="Sue"})

Now you don't have to remove and add the item to update it:

(From UserInfo In Users Where UserInfo.ID = 3 Select UserInfo).First.Name = "Susan"

Despite everything, the person most likely to be fooling you next is yourself.

[Chinners]

Hi Guffa, Thanks for the reply - some very useful information in there. I do have one small problem though - I cant find the correct syntax for the update:

(From UserInfo In Users Where UserInfo.ID = 3 Select UserInfo).First.Name = "Susan"

It doesnt work on its own in VB 2k8, and after hours of net searching, I cant find the answer :((. Using:

dim b as boolean = (From UserInfo In Users Where UserInfo.ID = 3 Select UserInfo).First.Name = "Susan"

compiles, but obviously doesnt update anything (the expression above supposedly returns a boolean) If you get chance, and you know the answer, can you post a quick message telling me... Ta muchly!

[Guffa]

I thought that the LINQ expression could be used as an expression, but obviusly it can't. If you put the result in a variable, it works:

Dim user As UserInfo = (From u In Users Where u.ID = 3 Select u).First
user.Name = "Susan"

Another way to do this (and more effective as it only looks until it finds the first occurance) is to use a lambda expression:

Users.Find(Function(u) u.ID = 3).Name = "Susan"

Despite everything, the person most likely to be fooling you next is yourself.

[Chinners]

Hi Guffa, Thanks for that - you have been a huge help! I cant believe I didnt try option 1 first though :doh: I think I tried everything but!