How to pass value to sql command in c# -

i have sql command:

string keyprocesses = "select distinct stuff((select ', '+ cn.name  wmccmcategories cn  inner join categorysets uc on uc.categoryid = cn.categoryid inner join keyprocesses u on u.categorysetid = uc.setid  inner join companies c on c.companyid = u.companyid  c.companyname = @companyname  order cn.name xml path('')), 1, 1, '') liststr wmccmcategories cnn group cnn.name"; 

and have:

public sqlcommand sqlcmd = new sqlcommand(); sqlcmd.commandtext = commandtext; //where commandtext sql statement sqlcmd.parameters.clear(); 

then execute connection:

string connectionstring = configurationsettings.appsettings["connectionstring"]; using (sqlconnection connection = new sqlconnection(connectionstring)) {     sqlcommand command = new sqlcommand(commandtext, connection);     try     {         connection.open();         sqldataadapter sdr = new sqldataadapter(sqlcmd.commandtext, connection);         datatable dt=new datatable();         sdr.fill(dt) 

after want move next sql command , add parameter command:

sqlcmd.commandtext = keyprocesses; sqlcmd.parameters.addwithvalue("@companyname", compnyname); sqldataadapter sdr1 = new sqldataadapter(sqlcmd.commandtext, connection); datatable dtb1 = new datatable(); sdr1.fill(dtb1); 

but fail execute sqlcommand. make sure sql key process can run fix parameter pre-added in. compnname not empty. suspect here how add value sql parameter. don't know wrong in way of using ?

edit: update whole part of code easy of investigating issue:

string connectionstring = configurationsettings.appsettings["connectionstring"];             using (sqlconnection connection = new sqlconnection(connectionstring))             {                 sqlcommand command = new sqlcommand(commandtext, connection);                  try                 {                     connection.open();                      sqldataadapter sdr = new sqldataadapter(sqlcmd.commandtext, connection);                     datatable dt=new datatable();                     sdr.fill(dt);                         //to store values of company names:                     list<companymodel> companies = new list<companymodel>();                           for(int = 0; < dt.rows.count; i++)                         {                             companies.add(new companymodel                              {                                  compnsn = + 1,                                 compnname =  dt.rows[i]["companyname"].tostring(),                                 compnaddress =  dt.rows[i]["address"].tostring()                             });                         }                          companyrepeater.datasource = companies;                         companyrepeater.databind();                          string comname = dt.rows[0]["companyname"].tostring();                         var names = companies.select(c => c.compnname);                          string[] arr = names.toarray();                         foreach (string compnyname in arr)                         {                             //to write names file debugging purpose                             using (streamwriter _testdata = new streamwriter(server.mappath("~/file.txt"), true))                             {                                  _testdata.writeline(compnyname); // write file.                             }                                 //get keyprocesses                               sqlcmd.commandtext = keyprocesses;                               //sqlcmd.parameters.addwithvalue("@companyname", compnyname);                               sqlcmd.parameters.add("@companyname", sqldbtype.nvarchar);                               sqlcmd.parameters["@companyname"].value = compnyname;                              // sqldataadapter sdr1 = new sqldataadapter(sqlcmd.commandtext, connection);                               datatable dtb1 = new datatable();                               //sdr1.fill(dtb1);                               using (var reader = sqlcmd.executereader())                               {                                   dtb1.load(reader);                               }                                companies.add(new companymodel                               {                                   compnkeyprocesses = dtb1.rows[0][0].tostring()                                }); 

frankly, don't need adapter here @ all. adds confusion. remove it:

sqlcmd.commandtext = keyprocesses; sqlcmd.parameters.addwithvalue("@companyname", compnyname); using(var reader = sqlcmd.executereader()) {     dtb1.load(reader); }