Self-Disposable (inline) declaration for C# disposable variable

Question

I can hardly believe the C# developers didnt thought about that. I dislike that there doesnt exist better way to create one-time disposable variables, as we have to declare them in blocks:

using( XYZ x = smth){
    ShowForm(Color.Blue, x,  "30px");
    ......
}

for me, placing the lines in brackets & placing declarations in-front of code, is visually unpleasent (as it reminds me to be if {} else {} block ).

so, does there exist any alternative way to create self-disposing variables inline, like:

ShowForm(Color.Blue, (using x=smth) x ,  "30px");

?

Answer 1

Not only does C# not have a facility for this, but it is also not possible to define one without getting into ambiguities with expression's semantic.

The limits of the using block define the scope of the newly added variable, along with its useful lifetime. The closing brace of the using block (or the end of a single statement when it is not enclosed in curly braces) defines the point where Dispose must be called on the object of the using clause.

Now imagine that there is such a thing as a using expression that lets us create a disposable object "inline", e.g.

ShowForm(Color.Blue, using var x = smth,  "30px");

What should be the useful lifetime of x? Should it be disposed when ShowForm returns? What if you do this

Foo(1, Bar(2, using var x = smth))

should x be disposed when Bar finishes, or should it wait for Foo to complete as well?

There are other contexts, such as control expressions of loops and conditional statements, where the scope of disposable variable would become ambiguous. That is why C# insists on providing explicit limits to the scope of the disposable variable introduced in the using clause.