Using (keyword)

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The using statement provides the combined functionality of "with" and a "try/finally" block to Dispose a resource automatically after using it.

Example

using f := new FileStream(...) do begin
  ...
end;

The above code is equivalent to:

with f := new FileStream(...) do try
  ...
finally

  if (f is Idisposable) then (f as IDisposable).Dispose();
end;

Important: the object in the "using" statement must be a construct that supports the standard .NET IDisposable interface, if it doesn't, or if the value is nil, it will ignore it and skip the Dispose call.

.NET's Garbage Collector (GC) manages memory usage but does not handle resources such as file handles. In order to free files for others to access, you need to dispose of such objects. See Finalizers for more information.

Remarks

A "using variable", that might potentially hide another local variable will yield a compilation error.

var a := 1;

using a := connection.CreateCommand do
begin
end;

If a happened to be a field of this class, it would only yield a PW12 warning (name clash).

See Also

• With (keyword)
• Expressions

Area: Oxygene Language
Compiler version: Oxygene 5

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