SAS include code into data step

I have dynamically create a myfile.sas with following content:

and a = 0
and b = 0

Now I want to include this file into a data step:

data y;
   set x;

   if 1=1 
      %include incl("myfile.sas")
   then selektion=0;
   else selektion=1;
run;

The result should be:

data y;
   set x;

   if 1=1 
      and a=0
      and b=0
   then myvar=0
   else myvar=1;
run;

However I get the following error:

ERROR 388-185: Expecting an arithmetic operator.
ERROR 200-322: The symbol is not recognized and will be ignored.

Is this possible to include the file into the if statement?

Indeed, that doesn't work. You can use %include within a data or proc step to add some lines to it but not within an incomplete statement.

Had your myfile.sas looked like this:

if 1=1
and a = 0
and b = 0

you could have written

data y;
   set x;
   %include "myfile.sas";;
   then selektion=0;
   else selektion=1;
run;

Couldn't you have these lines in a macro instead of a file?

%macro mymacro;
  and a=0
  and b=0
%mend;

data y;
   set x;
   if 1=1 
      %mymacro
   then selektion=0;
   else selektion=1;
run;

If that myfile.sas has to stay as is, you could work around it in this rather convoluted (but still generic) way:

filename myfile temp;

data _null_;
file myfile2;
infile 'myfile.sas' eof=end;
input;
if _n_=1 then put '%macro mymacro;';
put _infile_;
return;
end:
  put '%mend;';
run;
%include myfile;

data y;
   set x;
   if 1=1 
      %mymacro
   then selektion=0;
   else selektion=1;
run;