c# - How to dynamically create a lambda expression -

let's suppose have following class:

public class show {     public string language { get; set; }     public string name { get; set; } } 

based on information, goal create lambda expression this:

g => g.language == lang && g.name == name 

lang , name local variables add constant values when creating expression.

as can see, compiled function of type func<genre, bool>

to understand more clearly, achieve similar this:

string lang = "en"; string name = "comedy"; genre genre = new genre { language = "en", name = "comedy" }; expression<func<genre, bool>> expression = createexpression(genre, lang, name); // expression = (g => g.language == "en" && g.name == "comedy") 

i aware of existence of expression trees i'm pretty new topic don't know how start.

can problem solved? how can create such expression dynamically?

public expression<func<tvalue, bool>> createexpression<tvalue, tcompare>(tvalue value, tcompare compare) {     var pv = expression.parameter(typeof(tvalue), "data");     var compareprops = typeof(tcompare).getproperties();      // first statement of expression     expression exp = expression.constant(true);      foreach (var prop in typeof(tvalue).getproperties())     {         // check if compare type has same property         if (!compareprops.any(i => i.name == prop.name))             continue;          // build expression: value.propertya == "a"          // "a" come compare.propertya         var eq = expression.equal(             expression.property(pv, prop.name),              expression.constant(compareprops                 .single(i => i.name == prop.name)                 .getvalue(compare)));          // append first (previous) statement         exp = expression.andalso(exp, eq);     }      return expression.lambda<func<tvalue, bool>>(exp, pv); } 

usage:

var value = new { lang = "en", name = "comedy"};  // comparevalue should have same property name value,  // or expression ignore property var comparevalue = new { lang = "en", name = "comedy", other = "xyz" };  // create expression content // {data => ((true andalso (data.lang == "en")) andalso (data.name == "comedy"))} bool ismatch = createexpression(value, comparevalue).compile()(value); // true