C#•3mo ago

Can someone explain why these nested `using` is different from the ordinary one?

zxa4fd · 2024-04-19T14:29:52.963Z

How is this: ```cs using(resource1) using(resource2) { // Code here } ``` different from: ```cs using(resource1) { using(resource2) { // Code here } } ```

How is this:

using(resource1)
using(resource2) 
{
    // Code here
}

using(resource1)
using(resource2) 
{
    // Code here
}

different from:

using(resource1) 
{
    using(resource2)
    {
    // Code here
    }
}

using(resource1) 
{
    using(resource2)
    {
    // Code here
    }
}

5 Replies

Jimmacle•3mo ago

it's not

zxa4fd•3mo ago

I think they are. I remember that some streams were not behaving correctly if I don't use the second one. I think they have different scopes?

Jimmacle•3mo ago

the only change is no braces for the first using statement, which is fine as long as you only have one statement in it (which you do in this example, another using) it's the same rules for other statements like

if (thing1)
  if (thing2)
    DoThingIfThing1AndThing2AreTrue();

if (thing1)
  if (thing2)
    DoThingIfThing1AndThing2AreTrue();

reflectronic•3mo ago

the reason you can do

using (resource1)
using (resource2)

using (resource1)
using (resource2)

is exactly for the same reason you can do

using (resource1)
    // Code here

using (resource1)
    // Code here

it is not special behavior, it is just that you can remove the braces for an embedded statement it works identically to the version with the braces

Jimmacle•3mo ago

not directly related but using declarations may be more convenient for you regardless unless you actually need to control the lifetime of the object within the method

using var thing = GetResource();

using var thing = GetResource();

will automatically dispose the object at the end of the scope it's declared in

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Can someone explain why these nested `using` is different from the ordinary one?