c# - DataGrid replaces first row instead of adding a new row, -

i have datagrid in wpf populated observablecollection on doubleclick form datagrid (users click on preferred title , details datagrid populated associated data).

every time search new title, , make selection, details datagrid replaces first row of data there. how make datagrid adds new row can log multiple entities @ once exporting?

my code bellow:

datagrid .cs

// action seach imdb api associated infromation imdbid tagged title chose in listbox.    private void movie_list_mousedoubleclick(object sender, routedeventargs e)             {           // grabs imdbid associated movie title selected used second api request.        // datarowview row = (datarowview)movie_list.selecteditems;           string titleid = ((searchinfo)movie_list.selecteditem).imdbid;         string newurl = "http://www.omdbapi.com/?i=" + titleid + "&r=xml";           // prepares 2nd api url request data chosen title.          // creates xml document  store xml data sent api.         var doc = xelement.load(newurl);           // creates xml noedlist store values going associated given attribute tag.         ienumerable<xelement> movielist = doc.descendants("movie");          // creats observablecollection object retrievalinfo displayed in movie_datagrid, can edited.         observablecollection<retrievalinfo> gridinfo = new observablecollection<retrievalinfo>(movielist.select(movieelement =>             new retrievalinfo()         {             title = movieelement.attribute("title").value,             actors = movieelement.attribute("actors").value.split(',').tolist(),             genre = movieelement.attribute("genre").value,             rated = movieelement.attribute("rated").value,             imdbrating = movieelement.attribute("imdbrating").value,             released = movieelement.attribute("released").value,             runtime = movieelement.attribute("runtime").value,         }));         movie_datagrid.itemssource = gridinfo;            } 

retrievalinfo class (object used observablecollection)

public class retrievalinfo {     public retrievalinfo()     {         actors = new list<string>();     }      //creating list of info objects store returned data selected title.     public string title { get; set; }     public list<string> actors { get; set; }     public string genre { get; set; }     public string rated { get; set; }     public string imdbrating { get; set; }     public string released { get; set; }     public string runtime { get; set; }     } } 

datagird xaml (movie_datagrid, holds details of movie selected)

<datagrid x:name="movie_datagrid"             grid.columnspan="2"             horizontalalignment="left"             margin="292,107,0,0"             verticalalignment="top"             height="214"             width="673"             autogeneratecolumns="false"             itemssource="{binding gridinfo}">                 <datagrid.columns>                     <datagridtextcolumn header="title" binding="{binding path=title}"/>                     <datagridtextcolumn header="main actor 1" binding="{binding path=actors[0]}"/>                     <datagridtextcolumn header="main actor 2" binding="{binding path=actors[1]}"/>                     <datagridtextcolumn header="main actor 3" binding="{binding path=actors[2]}"/>                     <datagridcomboboxcolumn header="digital format" itemssource="{binding digital}"/>                     <datagridcomboboxcolumn header="physical format" itemssource="{binding physical}"/>                     <datagridtextcolumn header="genre" binding="{binding path=genre}"/>                     <datagridtextcolumn header="rated" binding="{binding path=rated}"/>                     <datagridtextcolumn header="imdb rating" binding="{binding path=imdbrating}"/>                     <datagridtextcolumn header="released" binding="{binding path=released}"/>                     <datagridtextcolumn header="runtime" binding="{binding path=runtime}"/>                     <datagridcomboboxcolumn header="file type" itemssource="{binding file_type}"/>             </datagrid.columns>         </datagrid> 

before binding datagrid, should existing items list , add new item list , bind datagrid.

 list<retrievalinfo> gridinfo = (list<retrievalinfo>)movie_datagrid.itemssource; 

add new item list,

gridinfo.add(new retrievalinfo()); 

then bind list datagrid,

 movie_datagrid.itemssource = gridinfo;