c# - Calling a generic function when type is only known at execution time -

i have generic function looks this:

public static class excelimport {     public static list<t> test<t>(string filename, string worksheetname) t : class     {         return new list<t>(excelimport.parse<t>(filename, worksheetname));     }     ... } 

if know on type of objects perform test function, can call way (for example):

list<oee.data.equipment> result = excelimport.test<oee.data.equipment>(filename.text, worksheetname.text); 

but fact test can applied class of oee.data namespace , users select right class in combobox before launching test function.

i use switch link different call each combobox value means i'll have had new cases anytime i'll add classes oee.data. so, how can give type dynamically? code below not working:

list<type.gettype("oee.data.equipment")> result = excelimport.test<type.gettype("oee.data.equipment")>(filename.text, worksheetname.text); 

thanks in advance!

simon

edit: in answer comment under dishold's response, here code that's behind call test method:

public static list<t> test<t>(string filename, string worksheetname) t : class {     return new list<t>(excelimport.parse<t>(filename, worksheetname)); }  private static ienumerable<k> parse<k>(string filename, string worksheetname) k : class {     ienumerable<k> list = new list<k>();     string connectionstring = string.format("provider=microsoft.jet.oledb.4.0; data source={0};extended properties=excel 8.0;", filename);     string query = string.format("select * [{0}]", worksheetname);      dataset data = new dataset();      using (oledbconnection con = new oledbconnection(connectionstring))     {         con.open();         oledbdataadapter adapter = new oledbdataadapter(query, con);         adapter.fill(data);         list = populatedata<k>(data);     }      return list; }  private static list<t> populatedata<t>(dataset data) t : class {     list<t> dtos = new list<t>();      foreach (datarow row in data.tables[0].rows)     {         t dto = activator.createinstance<t>();          populatefieldsfromdatarows(row, dto);         dtos.add(dto);     }      return dtos; } 

the new problem in method populatedata, because can't create instance of system.runtimetype here:

t dto = activator.createinstance<t>(); 

try this:

type type = type.gettype("oee.data.equipment"); methodinfo genericmethod = typeof(excelimport).getmethod("test").makegenericmethod(new type[]{type}); object result = genericmethod.invoke(null, new[]{filename.text, worksheetname.text}); 

update:

in example using sql database, can convert oledb. have sql database has table customer.

it has: id uniqueidentifier, name varchar(100), age int, email varchar(100).

then created class called customer:

    public class customer     {         public guid id { get; set; }          public string name { get; set; }          public string email { get; set; }          public int age { get; set; }     } 

i think know kind of result query. create class has properties matches query fields(like customer). can assign using linq. let me know if have trouble understanding code.

            sqlconnection conn = new sqlconnection("data source=localhost;initial catalog=test;integrated security=true");             conn.open();             sqlcommand command = new sqlcommand("select * customer", conn);             dataset dataset = new dataset();             sqldataadapter adapter = new sqldataadapter(command);             adapter.fill(dataset);             var = (from d in dataset.tables[0].rows.cast<datarow>()                     select new customer() {                         id = (guid)d[0],                         name = d[1].tostring(),                         age = convert.toint32(d[2]),                          email = d[3].tostring()                     }).tolist(); 

i hope helps,