c# - combine predicates into expression -

i aiming use signature:

ienumerable<t> searchfor(expression<func<t, bool>> expression); 

and , these 2 predicates:

func<employee, bool> isactiveemployee = e => e.datefired == null; func<employee, bool> isnewemployee = e => e.datehired >= datetime.today.adddays(-90); 

into expression. how can achieve please?

ps:

basically, trying use this. line:

var body = (binaryexpression) expression.body; 

in method getdynamicquery taken here throws exception:

unable cast object of type 'system.linq.expressions.instancemethodcallexpressionn' type 'system.linq.expressions.binaryexpression'.

using approach:

expression<func<employee, bool>> isactiveemployee = e => e.datefired == null; expression<func<employee, bool>> isnewemployee = e => e.datehired >= datetime.today.adddays(-90);  expression<func<employee, bool>> combined_expression = e => isactiveemployee.invoke(e) && isnewemployee.invoke(e); 

i assuming need real expression can translated sql many data access frameworks.

one solution use linqkit this:

expression<func<employee, bool>> isactiveemployee = e => e.datefired == null; expression<func<employee, bool>> isnewemployee = e => e.datehired >= datetime.today.adddays(-90);  expression<func<employee, bool>> combined_expression = e => isactiveemployee.invoke(e) && isnewemployee.invoke(e); 

then can wrap iqueryable using asexpandable method linqkit this:

var query = context.employees.asexpandable().where(combined_expression); 

or, if don't want invoke asexpandable, can expand new expression , use other expression this:

expression<func<employee, bool>> combined_expression = e => isactiveemployee.invoke(e) && isnewemployee.invoke(e);  combined_expression = combined_expression.expand();  var query = context.employees.where(combined_expression); 

update:

for second example provided, can this:

expression<func<employee, bool>> expression1 = e => e.guid == new guid("28d3bcfb-9472-4141-bd88-be5e7e1230f0");  expression<func<employee, bool>> expression2 = e => e.guid == new guid("0f0dba45-f842-4e46-9ed4-f50b5bcf0509");  expression<func<employee, bool>> combined_expression = e => expression1.invoke(e) || expression2.invoke(e);  combined_expression = combined_expression.expand();  // use combined_expression