C#•17mo ago

❔ Filter list with lambda expression?

Hello! Right now I have a "MyList = blahaRepo.GetAllUsers();" which retrieves all users. Instead of creating a separate method for retrieving users with a specific flag or creating a new list and run a foreach and add those with the specific flag to the new list - Can I simply use a lambda expression along with the line above to filter out while filling the first list? Or is there a better way to filter out the data?

23 Replies

Cattywampus•17mo ago

you can use the built in .FindAll method

Cattywampus•17mo ago

https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1.findall?view=net-8.0

List.FindAll(Predicate) Method (System.Collections.Generic)

Retrieves all the elements that match the conditions defined by the specified predicate.

Ice_•17mo ago

So like GetAllUsers().FindAll(...)? Oooh On the List. Of course Thank you!

Cattywampus•17mo ago

goodluck

Ice_•17mo ago

Thanks!

Cattywampus•17mo ago

tho Linq would be a better choice here... but it's up to you

ero•17mo ago

WhereAsync right

Ice_•17mo ago

I used Linq. Basically filtered it out whenever I needed it: @foreach (var item in UserList.FindAll(x=>x.Admin==true))

ero•17mo ago

that's not linq but if it works that's great

Ice_•17mo ago

Sorry, lambda

ero•17mo ago

i would suggest maybe choosing some better variable names

@foreach (var user in UserList.FindAll(u => u.IsAdmin))

@foreach (var user in UserList.FindAll(u => u.IsAdmin))

Ice_•17mo ago

Yeah, I'm going to work with naming conventions a bit later. It's just test code right now Thanks!

Angius•17mo ago

If you're using EF, this will load all the users and then filter them What you want is to include a .Where() in your EF query

Ice_•17mo ago

It's EF. And exactly It's loading everything from a database server. I know it's not effecient loading every user from the list. Can you give me an example of using .Where? And whwre would I use it? When using dbcontext?

Angius•17mo ago

var users = await _context.Users
    .Where(u => u.ShoeSize > 32)
    .ToListAsync();

var users = await _context.Users
    .Where(u => u.ShoeSize > 32)
    .ToListAsync();

For example this will select all users that have their shoe size bigger than 32

Ice_•17mo ago

That really limits the data! The "problem" I am having is that I want to create two tables (html <table>), differenting between between ordinary and admin users. Using a LInq sort of makes me want to create two lists? But that is maybe the best way?

Aaron•17mo ago

FindAll would've created two lists actually, it would've made 3 the original list, a list of normal users, and a list of admin users

Angius•17mo ago

GroupBy() should translate to SQL, IIRC?

Ice_•17mo ago

I guess. Under the hood. So you mean that there isn't any more efficient way to do things in this case?

Aaron•17mo ago

^ GroupBy probably if it exists for IQueryable i'd assume it would work fine

Ice_•17mo ago

Alright! Thanks! I'm having an issue with Blazor and its components. You don't happen to know some stuff about that? <PageTitle> is literally being overwritten by one or more sub-components. I've tried googling the crap out of that but not found anything valuable 🤔

ero•17mo ago

open a new thread? this seems unrelated

Accord•17mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Filter list with lambda expression?