c# - LINQ Filter Implementation with Expressions -

in mvc4 , providing search box user search value in table. implementing generic filter condition @ server side in c#

need combine multiple expressions form single expression

 expression<func<t, bool>>  

for example

table columns

menutext, role name (role.name mapping), actionname

now if user entered in search box abc , can in of rows in shown columns, need filter.

model

public class menu {   public string menutext {get;set;}   public role role {get;set;}   public string actionname {get;set;} }  public class role {   public string name {get;set;} } 

so far have implemented

  /// <summary>     /// string[] properties property.name (menutext, actionname), including deeper mapping names such (role.name)     /// </summary>     public static expression<func<t, bool>> filterkey<t>(string filtertext, params string[] properties)     {         parameterexpression parameter = expression.parameter(typeof (t));         expression[] propertyexpressions = properties.select(             x => !string.isnullorempty(x) ? getdeeppropertyexpression(parameter, x) : null).toarray();          expression<func<t, bool>> predicate = predicatebuilder.false<t>();         foreach (expression expression in propertyexpressions)         {              var tolower = expression.call(expression, typeof(string).getmethod("tolower", system.type.emptytypes));             var = expression.call(tolower, typeof(string).getmethod("contains"), expression.constant(filtertext.tolower()));             //todo: combine expressions form single  expression<func<t, bool>> expression          }         return predicate;     }         /// <summary>         ///  deeper properties such role.name expressions         /// </summary>        private static expression getdeeppropertyexpression(expression initialinstance, string property)         {             expression result = null;             foreach (string propertyname in property.split('.'))             {                 expression instance = result ?? initialinstance;                 result = expression.property(instance, propertyname);             }             return result;         } 

i have created few search iqueryable extension methods should able use

full blog post here:

http://jnye.co/posts/6/c%23-generic-search-extension-method-for-iqueryable

github project here (has couple of extensions or searches:

https://github.com/ninjanye/searchextensions

public static class queryableextensions   {       public static iqueryable<t> search<t>(this iqueryable<t> source, expression<func<t, string>> stringproperty, string searchterm)       {           if (string.isnullorempty(searchterm))           {               return source;           }            // below represents following lamda:           // source.where(x => x.[property] != null           //                && x.[property].contains(searchterm))            //create expression represent x.[property] != null           var isnotnullexpression = expression.notequal(stringproperty.body, expression.constant(null));            //create expression represent x.[property].contains(searchterm)           var searchtermexpression = expression.constant(searchterm);           var checkcontainsexpression = expression.call(stringproperty.body, typeof(string).getmethod("contains"), searchtermexpression);            //join not null , contains expressions           var notnullandcontainsexpression = expression.andalso(isnotnullexpression, checkcontainsexpression);            var methodcallexpression = expression.call(typeof(queryable),                                                      "where",                                                      new type[] { source.elementtype },                                                      source.expression,                                                      expression.lambda<func<t, bool>>(notnullandcontainsexpression, stringproperty.parameters));            return source.provider.createquery<t>(methodcallexpression);       }   }   

this allows write like:

string searchterm = "test";   var results = context.menu.search(menu => menu.menutext, searchterm).tolist();    //or role name string searchterm = "test"; var results = context.menu.search(menu => menu.role.name, searchterm).tolist(); 

you might find following posts useful:

search extension method allows search accros multiple properties:

http://jnye.co/posts/7/generic-iqueryable-or-search-on-multiple-properties-using-expression-trees

search extension method allows multiple or search terms on property:

http://jnye.co/posts/8/generic-iqueryable-or-search-for-multiple-search-terms-using-expression-trees