Essentially I had an endpoint that can take multiple query string params, most are optional, so I want to check first if the query parameter exists - then if it does "add" it to the query. This keeps to be sending me errors and doesn't feel efficient; have I missed something?

```cs
var query = _context.Things.AsQueryable();

if (data.Name is {} name) {
    query = query.Where(t => t.Name == name);
}
if (data.Age is > 0 age) {
    query = query.Where(t => t.Age == age);
}
if (data.SortBy is not null) {
    query = query.OrderBy(a => a.Something);
}

var things = await query.ToListAsync();
```

Ahh, so build the queryable; then it is <a:airquoteleft:898198984366096434> called <a:airquoteright:898199002728763442> when you `.ToListAsync()`

`.ToListAsync()`, `.FirstOrDefaultAsync()`, `CountAsync()` etc. are where the query gets resolved

So I guess my current impl, is just executing the query then I'm transforming the shape of the data based on my rules?

Your current code doesn't really do anything

Since the query doesn't get modified in place

You just call the `.Where()` on the query... and discard it

Good:
```cs
query = query.Where(...);
```
Bad:
```cs
query.Where(...);
```

All those methods — besides the ones that resolve the query — return an `IQueryable`, they're not `void`

help

We are a programming server aimed at coders discussing everything related to C# (CSharp) and .NET.

C#

help

How do I 'build' a QUERY with EF Core?