c# - Get dynamic OrderBy in LINQ -

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• dynamically sorting linq 9 answers

i using datatables in quite few pages in asp.net mvc 3 site. use server side paging , want implement sorting based on column headers. datatables comes isortcol_0 int value of column clicked.

i did not approach query end like:

if(isortcol_0 == 0) {         // query     // oderby(x => x.carname) } 

then repeated each column (plus else clause on each order descending). have changed approach , pass column name server.

i have come following:

expression<func<vw_car, string>> sortexpression1 = null; expression<func<vw_car, int>> sortexpression2 = null;  switch(columntosort)  {     case "invoiceno": sortexpression1 = x => x.carno; break;     case "clientnumber": sortexpression1 = x => x.forename; break;     case "clientname": sortexpression1 = x => x.surname; break;     default: sortexpression2 =  x => x.age.value; break; }  // start of query .orderbydir(sortdirection, sortexpression1 , sortexpression2) 

now orderbydir looks below:

public static iorderedqueryable<t> orderbydir<t>(this iqueryable<t> source, string dir, expression<func<t, string>> column1, expression<func<t, int>> column2) {     if (column1 != null)     {         return dir == "asc" ? source.orderby(column1) : source.orderbydescending(column1);     }              if (column2 != null)     {         return dir == "asc" ? source.orderby(column2) : source.orderbydescending(column2);     }         return null; } 

this works in sorts columns of type string or int. have column of datetime want sort, need write sortexpression3 , add orderbydir.

however don't implementation - had attempted write generic sort expression took object second parameter instead of string, int, datetime, when had code in place, getting unable cast type 'system.datetime' type 'system.object'. linq entities supports casting entity data model primitive types.

any 1 ideas possible better approach this?

such extension should fits needs:

public static class linqextensions {     public static iorderedqueryable<t> orderby<t>(this iqueryable<t> source, string property)     {         return applyorder(source, property, "orderby");     }      public static iorderedqueryable<t> orderbydescending<t>(this iqueryable<t> source, string property)     {         return applyorder(source, property, "orderbydescending");     }      private static iorderedqueryable<t> applyorder<t>(iqueryable<t> source, string property, string methodname)     {         var props = property.split('.');         var type = typeof(t);         var arg = expression.parameter(type, "x");         expression expr = arg;         foreach (var prop in props)         {             // use reflection (not componentmodel) mirror linq             var pi = type.getproperty(prop);             expr = expression.property(expr, pi);             type = pi.propertytype;         }         var delegatetype = typeof(func<,>).makegenerictype(typeof(t), type);         var lambda = expression.lambda(delegatetype, expr, arg);          var result = typeof(queryable).getmethods().single(                 method => method.name == methodname                         && method.isgenericmethoddefinition                         && method.getgenericarguments().length == 2                         && method.getparameters().length == 2)                 .makegenericmethod(typeof(t), type)                 .invoke(null, new object[] { source, lambda });         return (iorderedqueryable<t>)result;     } } 

invoke example:

query.orderby("age.value");