.net - Only parameterless constructors and initializers are supported in LINQ to Entitier in dropdown -

i have controller

public actionresult create() {     var db = new mydbcontext();     ienumerable<selectlistitem> items = db.fileuploadcategories          .select(c => new selectlistitem {             value = c.parentcategoryid.tostring(),             text = "--" + c.categoryname         });      viewbag.categories = items;     return view(); } 

and view this

 @html.dropdownlist("parentcategoryid", (ienumerable<selectlistitem>)viewbag.categories, "-- select --", new { @class = "form-control" }) 

this gives me result on website

<select> <option value="0">test</option> <option value="1">test</option> <option value="1">test</option> <option value="2">test</option> <option value="2">test</option> </select> 

as can see, value same, because parentcategoryid controller same correct. add "-" in text each text in options determined how large value is. want add 3 ' - ' in text if value 3 , if value five, want add 5 '-----' before test in text. want result similar this.

<select> <option value="0">test</option> <option value="1">-test</option> <option value="1">-test</option> <option value="2">--test</option> <option value="2">--test</option> </select> 

notice lines before test.

i have tried update controller to

text = new string('-',c.parentcategoryid) + c.categoryname 

which gives me error message

an exception of type 'system.notsupportedexception' occurred in entityframework.sqlserver.dll not handled in user code

additional information: parameterless constructors , initializers supported in linq entities.

you query needs able represented sql statement, new string('-',c.parentcategoryid) can't be. materialize query list<t> first

var items = db.fileuploadcategories.tolist().select(c => new selectlistitem() {     value = c.parentcategoryid.tostring(),     text= string.format("{0}{1}", new string('-',c.parentcategoryid), c.categoryname) }).tolist();