using with object type

Question

I try to write the following code and get an error

using (object obj = await command.ExecuteScalarAsync())
{
   //....
}

Implicitly convertible to System.IDisposable

How to solve that? I tried the cast (the static one doesn't work...)
If I don't use using and check that the object is not null I do the casting in the following way:

Convert.ToInt32(obj);

But I should use using

Answer 1

You don't need to dispose in this case, simply do:

object obj = await command.ExecuteScalarAsync();

ExecuteScalarAsync returns a Task<T>, which you are subsequently awaiting. This "awaiting" will handle the task object, you get the result from the task/execution, which is very unlikely to require disposal.

Answer 2

Using statement is only valid (and useful) with IDisposable objects. It gives you nothing if your object is not disposable. Basically, it's syntactic sugar for this equivalent code:

IDisposable obj = ...;
try
{
  ...
}
finally
{
  obj.Dispose();
}

The guys implementing the C# compiler simply decided that having the using statement available for classes that don't implement IDisposable would be useless and confusing.

It doesn't work in any way as with or some other statement that looks superficially similar. It will not affect garbage collection in any way (apart from perhaps limiting variable scope - but simple blocks ({ ... }) to the very same thing.

Safely getting the value is something completely different. You want to do something like this:

object val = await command.ExecuteScalarAsync();

if (val == DBNull.Value)
{
  // It's null
}
else
{
  int realValue = (int)val;
}