c# - Returning Expression<> using various class properties -

i have this:

public expression<func<message, bool>> filterdata() {     switch (this.operatorenum)     {         case filterparameteroperatorenum.equalto:             return message => !string.isnullorempty(message.body) &&                               message.body                                      .equals(this.value, stringcomparison.invariantcultureignorecase);          case filterparameteroperatorenum.notequalto:              return message => !string.isnullorempty(message.body) &&                               !message.body                                      .equals(this.value, stringcomparison.invariantcultureignorecase);          case filterparameteroperatorenum.contains:              return message =>                     !string.isnullorempty(message.body) &&                     message.body.indexof(this.value,                                    stringcomparison.invariantcultureignorecase) >= 0;          case filterparameteroperatorenum.doesnotcontain:             return message =>                     !string.isnullorempty(message.body) &&                     message.body.indexof(this.value,                                    stringcomparison.invariantcultureignorecase) == -1;       } } 

as can see done on message.body

i same thing on other string properties on message class , don't want duplicate code.

is there way passing in property somehow?

you can try composing expression manually, give ability specify property name string. isn't complete solution , it's untested, may give starting point see mean:

var parameter = expression.parameter(typeof(message), "o"); var getname = expression.property(parameter, "body");  var isnullorempty = expression.not(expression.call(typeof(string), "isnullorempty", null, getname)); var compare = expression.equal(getname, expression.constant("thisvalue"));  var combined = expression.and(isnullorempty, compare);  var lambda = expression.lambda(combined, parameter); 

so change function accept "body" parameter, , cast lambda @ end to:

expression<func<message, bool>> 

i may not have got syntax creating lambda right though.